A former Bavarian police officer and his wife were temporarily detained and their home was searched in connection with an investigation into a series of far-right death threats emailed to left-wing lawmakers, Frankfurt prosecutors said Monday.

Prosecutors said they had on Friday detained a 63-year-old former police officer and his 55-year-old wife, whose names were not revealed in line with German privacy policy, in the Bavarian town of Landshut. The man allegedly has a record for previous far-right criminal offenses, the German news agency dpa reported.

The two are suspected of sending multiple emails to parliamentarians and others, and were released after evidence had been secured from their home, dpa reported. Frankfurt prosecutors did not immediately respond to a request for more details.

Several politicians with the opposition Left Party and others have been the target of the threatening mails signed “NSU 2.0” — an apparent reference to the National Socialist Underground, a neo-Nazi group that killed 10 people, mostly with immigrant roots, between 2000 and 2007.

The case has raised concerns about possible extremists within the police, after it emerged that personal data used in a recent threat against a Left Party politician was accessed via a police computer in Hesse, the state in which Frankfurt is located, which prompted the resignation of the state police chief earlier this month.

In 2018, several threatening messages signed “NSU 2.0” were also sent to a Frankfurt lawyer representing victims’ families in the trial of the original NSU’s only surviving member.

Hesse state police are investigating 69 right-wing threat mails sent to 27 people and institutions in eight different states, according to state Interior Minister Peter Beuth.

It has not yet been determined whether all the letters were sent by the same person.