A suspected underground gas explosion ripped open roads and flipped vehicles in the heart of South Africa’s biggest city, killing one man and injuring at least 41 people, authorities and emergency services said on Thursday.

The cause of the blast, which happened during Wednesday’s evening rush hour in downtown Johannesburg, remained unclear. The company that supplies gas to that part of the city said it did not believe its underground pipelines were responsible, as authorities first thought.

The body of the deceased was found during a nighttime search of the blast area, Johannesburg’s Emergency Management Services spokesperson Robert Mulaudzi said on Twitter.

An investigation was under way as city authorities brought in specialists to determine whether other underground pipes or cables were in the area and if there was a threat of another explosion or gas leak.

“We are still searching for the source,” said Panyaza Lesufi, the premier of the Gauteng province where Johannesburg is located.

Lesufi said 12 people remained in several Johannesburg hospitals for medical treatment. The other 36 people who were hurt had been discharged, he said.

Some people were evacuated from the area on Wednesday night due to fears of a second explosion or that multi-storey buildings in a downtown section of the city might collapse. Lesufi said the damage was “extensive”.

However, people returned to the busy area in Johannesburg’s central business district on Thursday morning, either to return to their homes or get to work.

Authorities estimated that an area covering five city blocks was damaged and at least six roads were affected. At least 34 vehicles were damaged, with some flipped on their sides or lying on top of other vehicles. Others had tumbled into gaping crevices that appeared in the middle of roads as the damage resembled a scene from an apocalyptic movie.

Most of the damaged vehicles were minibus taxis, one of South Africa’s most popular commuting methods. Witnesses said some people were sitting in the minibuses when the explosion threw them into the air.