Sniffer dogs search for clues in ashes of deadly Joburg CBD fire

Police with sniffer dogs searched on Friday through the gutted remains of a Johannesburg CBD apartment block as authorities stepped up investigations into the cause of a fire that killed more than 70 people.

Officers cordoned off areas around the run-down five-storey building that was destroyed  by a blaze in the early hours on Thursday in one of South Africa's worst such disasters in living memory.

Most bodies were burned beyond recognition and investigators will have to rely on DNA samples from friends and relatives to identify them, said Thembalethu Mpahlaza from Gauteng's forensic pathology services.

Only 12 of the 74 bodies recovered so far were identifiable by sight, he said.

"I am devastated," said block resident Wambali Kaunda, who lost his brother and niece in the fire. "We have been told if you are able to identify your family members you will be able to collect the bodies."

Kaunda said he was on the first floor and not far from the exit when the fire broke out so her managed to escape.

While household fires are common in Johannesburg, especially in poor areas, the incident has highlighted a housing crisis in one of the world's most unequal cities, with widespread poverty and joblessness.

The apartment block is owned by municipal authorities, but officials have struggled to provide a clear picture of who lived there, saying the block had been "invaded and hijacked" by unknown groups.

A provincial official said on Thursday some of those who died may have been renting from, or were being extorted by, criminal gangs in the hijacked buildings syndicates.

On Thursday President Cyril Ramaphosa said the fire was "great tragedy" and a wake-up call for South Africa to tackle its inner-city housing crisis.