A mayor and two others were shot to death as they were traveling in a municipal vehicle on a highway in Mexico's Gulf coast state of Veracruz, authorities said Thursday.

Prosecutors said Maricela Vallejo, the mayor of the Mixtla de Altamirano municipality, was with her husband and her driver in the SUV when they came under fire from behind and both sides. Authorities found 31 bullet casings.

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Mourners, some carrying candles, gather around the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

A mayor and two others were shot to death as they were traveling in a municipal vehicle on a highway in Mexico's Gulf coast state of Veracruz, authorities said Thursday.

A man carries a candle as mourners gather to greet the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

The killing came a day after a mayor was slain in the southwestern state of Michoacan. Eduardo Otlica Avilés of Nahuatzen was kidnapped and his body found hours later.

Mourners walk alongside the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, for her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners walk alongside the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, for her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners hug as the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, arrives for a wake at her aunt's house, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners hug as the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, arrives for a wake at her aunt's house, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners gather around the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners gather around the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners carry candles as they greet the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners carry candles as they greet the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

A woman places a flower on the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as mourners gather for her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

A woman places a flower on the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as mourners gather for her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Grieving friends and relatives gather around the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Grieving friends and relatives gather around the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

People hold candles beside the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

People hold candles beside the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Family members of slain mayor of Mixtla de Altamirano, Maricela Vallejo, and her husband, stand near the forensics office where their bodies were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the couple and their driver came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Family members of slain mayor of Mixtla de Altamirano, Maricela Vallejo, and her husband, stand near the forensics office where their bodies were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the couple and their driver came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police stand guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police stand guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police officers stand guard on the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz state, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police officers stand guard on the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz state, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

A municipal police officer stands guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

A municipal police officer stands guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Men carry the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as family and friends hold a wake for her in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Men carry the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as family and friends hold a wake for her in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

An armed policeman walks past a shop as residents watch the arrival of the hearse carrying the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, before her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

An armed policeman walks past a shop as residents watch the arrival of the hearse carrying the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, before her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

There was no immediate word on a possible motive.

Mourners, some carrying candles, gather around the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners, some carrying candles, gather around the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

The killing came a day after a mayor was slain in the southwestern state of Michoacan. Eduardo Otlica Avilés of Nahuatzen was kidnapped and his body found hours later.

Killings of politicians in Mexico rose last year during nationwide elections but then fell off.

Overall Mexico's homicides were up 9.7% in the first quarter of his year, compared with the same period in 2018.

A man carries a candle as mourners gather to greet the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

A man carries a candle as mourners gather to greet the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners walk alongside the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, for her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners walk alongside the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, for her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners hug as the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, arrives for a wake at her aunt's house, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners hug as the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, arrives for a wake at her aunt's house, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners gather around the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners gather around the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house for her wake, in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners carry candles as they greet the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Mourners carry candles as they greet the hearse bringing the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, to her aunt's house in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

A woman places a flower on the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as mourners gather for her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

A woman places a flower on the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as mourners gather for her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Grieving friends and relatives gather around the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Grieving friends and relatives gather around the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake held at her aunt's home where she grew up in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

People hold candles beside the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

People hold candles beside the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, during her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Family members of slain mayor of Mixtla de Altamirano, Maricela Vallejo, and her husband, stand near the forensics office where their bodies were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the couple and their driver came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Family members of slain mayor of Mixtla de Altamirano, Maricela Vallejo, and her husband, stand near the forensics office where their bodies were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the couple and their driver came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police stand guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police stand guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police officers stand guard on the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz state, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Municipal police officers stand guard on the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz state, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

A municipal police officer stands guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

A municipal police officer stands guard on the corner of the street where the forensic office is located, where the bodies of Mixtla de Altamirano Mayor Maricela Vallejo, her husband and her driver were taken in Orizaba, Veracruz, Mexico, Thursday, April 25, 2019. Prosecutors said the three came under fire from behind and both sides of their SUV while traveling on a highway. (AP PhotoFelix Marquez)

Men carry the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as family and friends hold a wake for her in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

Men carry the coffin of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, as family and friends hold a wake for her in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

An armed policeman walks past a shop as residents watch the arrival of the hearse carrying the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, before her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)

An armed policeman walks past a shop as residents watch the arrival of the hearse carrying the body of Maricela Vallejo, the slain 27-year-old mayor of Mixtla de Altamirano, before her wake in Zongolica, Veracruz state, Mexico, Thursday, April 25, 2019. Vallejo, her husband, and a driver were assassinated Thursday by multiple gunmen as they drove along a highway. (AP PhotoFelix Marquez)