Some people threw babies out of third-story windows to others waiting below in the desperate scramble to evacuate, witnesses said.

At least 12 of those killed were children, the youngest a 1-year-old, according to city and medical officials.

They said at a news conference that an undetermined number of people were still missing and many bodies recovered were burned beyond recognition.

More than 50 people were injured, six of whom were in a serious condition in the hospital.

Emergency services officials had earlier warned that the death toll could rise as they continued to search the scene more than 12 hours after the blaze broke out at around 1 a.m.

Dozens of bodies recovered by firefighters were laid out on a side road outside the apartment block, some in body bags, others covered in silver sheets or blankets after the body bags ran out. They were eventually taken away in pathology department vehicles.

“Over 20 years in the service, I’ve never come across something like this,” Johannesburg Emergency Services Management spokesperson Robert Mulaudzi said.

Authorities hadn’t established the cause of the fire but Mgcini Tshwaku, a local government official, said initial evidence suggested it started with a candle. Inhabitants used candles and fires for light and to keep warm in the winter cold, he said.

Firefighters were still making their way through the remnants of shacks and other informal structures that littered the inside of the derelict five-story building in the heart of Johannesburg’s central business district hours after the fire was extinguished. Smoke seeped out of the blackened building even though the fire was out, while twisted blankets and sheets hung like ropes out of shattered windows to show how people had used them to try and escape the flames.

Some of the survivors described how they jumped out of windows, but only after tossing their children to others below.

“Everything happened so fast and I only had time to throw the baby out,” said Adam Taiwo, who managed to save his 1-year-old son and himself. “I also followed him after they caught him downstairs.” Taiwo said he did not know where his wife, Joyce, was.

A witness who lives in a building across the road said he saw others also throw babies out of the burning building and that at least one man died when he jumped from the third floor and hit the concrete sidewalk “head first.”

Another witness who didn’t give his name told television news channel eNCA that he lived in a building next door and heard people screaming for help and shouting “We’re dying in here.”

As the fire raged, some occupants got trapped behind locked gates at the exits and there were no proper fire escape routes, local official Tshwaku said.

“People couldn’t get out,” he said, adding that some of the victims may have died after jumping out of the building.

More than 200 people were living in the building, witnesses said, including in the basement, which should have been used as a parking garage. Others estimated an even higher number of occupants.

Johannesburg mayor Kabelo Gwamanda said 141 families were affected by the tragedy but could not say exactly how many people were in the building when the fire started. Many of the people inside were foreign nationals, he said. That could make identifying victims and tracing the missing hard as many were likely in South Africa illegally, other officials said.

A woman who asked not to be identified said she lived in the building and escaped with her grown son and a 2-year-old child. She stood outside holding the toddler for hours and said she didn’t know what happened to two other children from her family.

“I just saw smoke everywhere and I just ran out with this baby only,” the woman said. “I don’t have any home, and I don’t know what to do anymore.”

In a statement, South African President Cyril Ramaphosa said, “this is a great tragedy felt by families whose loved ones perished in this awful manner, and our hearts go out to every person affected by this event.”