Onlookers gather at the scene following a suspected the gas leak. Photo: Reuters

At least 16 people, including three children, were killed by a leak of toxic nitrate gas reportedly being used by illegal miners to process gold South African police and local officials say.

Emergency services initially announced that as many as 24 people might be dead in the Angelo settlement in Boksburg, a city on the eastern outskirts of Johannesburg.

But police and Gauteng Province Premier Panyaza Lesufi later said the number of deaths had been confirmed as 16 after a recount of the bodies.

“It’s not a nice scene at all ... It’s painful, emotionally draining and tragic,” Lesufi, who visited the scene, was quoted as saying in news reports.

Teams were searching the area looking for other casualties deep into Wednesday night. “We can’t move anybody. The bodies are still where they are on the ground,” said emergency services spokesman William Ntladi.

A forensic investigator was seen covering the body of a small child with a blanket. Another body could be seen covered in a white cloth with a shoe sticking out. It lay under a strip of yellow police tape cordoning off the area, AP news agency reports.

Police said the three children killed included an infant and that two people were taken to the hospital for treatment.

Boksburg is the city where 41 people died after a truck carrying liquefied petroleum gas got stuck under a bridge and exploded on Christmas Eve.

Ntladi said Wednesday's deaths were caused by a nitrate gas that leaked from a gas cylinder being kept in a shack. He said the cannister had emptied out in the leak and teams were able to begin going over an area stretching out 100 meters (100 yards) from the cyclinder to check for more casualties.

Ntladi said the information authorities had indicated the cylinder that caused the leak was being used by illegal miners to separate gold from dirt and rock.

Authorities didn't say if the illegal miners they believed to be responsible for the gas leak were among the casualties. Illegal mining is rife in the gold-rich areas around Johannesburg, where miners go into closed off and disused mines to search for any deposits left over.

TRT Afrika and agencies