More than 70 people were killed overnight when fire raged through a five-storey apartment block in a poor area of Johannesburg, officials said on Thursday, adding that some of the victims may have been renting rooms there from criminal gangs.

At noon, the munipical-owned building was still smouldering, a large part of it blackened by soot, as emergency services gathered around it and bodies lay covered in blankets on a nearby street, a Reuters reporter said.

Leo, a 25-year-old who survived the blaze, had been living on the second floor. He escaped along with his mother via the stairs.

“People were just running away. It was dark and there was smoke. You couldn’t see anything,” he said.

At least one person jumped to their death, said Thando le Nkosi Manzini, a student who saw the blaze from the street. “I saw a guy jumping from the fourth floor,” he told Reuters.

The blaze, which started at around 1.30 a.m., killed at least 73 people and injured 43, the municipal government said, in one of South Africa’s worst such tragedies in living memory.

Johannesburg authorities initially suggested the building had been occupied by squatters.

But city Mayor Kabelo Gwamanda told reporters it was owned by the municipal authorities and had been leased to charity for displaced women but had “ended up serving a different purpose,” without giving further details.