A powerful blast ripped through a multistory building in Pakistan's southern port city of Karachi on Wednesday, killing at least three people and wounding 15 others, police and rescuers said.

It was not immediately clear what caused the blast, but it appeared to be an accidental explosion, likely caused by the ignition of a cooking gas canister.

Some people were still trapped under the rubble, according to Saad Edhi, a spokesman for the Edhi ambulance service. Sajid Sadozai, a senior police officer in Karachi, confirmed that three people had died.

Pakistan's troops and rescue workers look for survivors amid the rubble of a damaged building following the explosion, in Karachi, Pakistan, Wednesday, Oct. 21, 2020. Police and rescuers say a powerful blast has ripped through a multistory building in Pakistan’s southern port city of Karachi. (AP PhotoFareed Khan)

Pakistan's troops and rescue workers look for survivors amid the rubble of a damaged building following the explosion, in Karachi, Pakistan, Wednesday, Oct. 21, 2020. Police and rescuers say a powerful blast has ripped through a multistory building in Pakistan’s southern port city of Karachi. (AP PhotoFareed Khan)

TV footage showed rescuers digging through the remains of a collapsed building.