Authorities investigate the cause of the earth-shattering explosion on Bree Street.

Witnesses reported hearing a loud explosion as the road tore open and then alarms sounded from overturned taxis and injured passengers started screaming.

The cause of the disaster had, late on Wednesday night, yet to be ascertained.

“I heard a vibration from down [there],” said Vincent, a security guard at a residential building next to the explosion. “It was vibration for two seconds; then it blew up.”

Almost 100m of the busy roadway appeared to have been torn down the middle, with overturned vehicles littering the pavement. Dozens of disaster management personnel, firefighters and police attended the scene, attempting to enforce a cordon.

The overwhelming response was in stark contrast to previous incidents in Gauteng’s metros, such as the Boksburg tanker explosion that claimed 43 lives in late 2022.

“People have indicated from that side that they are starting to have headaches and chest pains,” said Gauteng Premier Panyaza Lesufi, who attended the scene.

While a gas line explosion was the suspected cause, gas lines run beneath the pavement, not under the roadway itself, and they operate at low pressure and thus are unlikely to cause an explosion, according to a statement issued by Egoli Gas, which manages the municipal lines in the city.

Egoli gas said its network had experienced no pressure loss which indicated that its pipelines were intact. It added that a team was on site to investigate whether there were any gas leaks but none had been found by the time of publishing.

An hour after the incident, what seemed to be a faint smell of gas lingered in the air.

Lesufi confirmed that a team from Egoli Gas was on the scene.

“They are on the scene to advise us on the evacuation, the nature of the gas, its effect, and what needs to happen when this kind of gas is inhaled,” he said.

Illegal mining operations are known to be conducted in and around the Johannesburg CBD and were also discussed as possible causes by police on the scene.

At least a dozen people, including a City Power employee, were transported to hospital with injuries ranging from minor to severe, according to messages and requests for assistance on local emergency services groups.

The degree of damage to neighbouring residences had not been ascertained.

“It [the road] was bursting,” said a witness, who filmed the incident on his phone. “I was waiting here on the corner. I don’t know what happened. The road just burst.”

Bystanders crowded around the police tape surrounding the disaster site, with many people receiving orders from disaster management services to leave their apartments. Private security and police escorted people out of nearby buildings.

“We still need to do some search and rescue,” said Johannesburg City Manager Floyd Brink.

“It’s not 100% clear exactly where [the cause of the explosion] is from.”

In a statement, City Power said services within the Johannesburg CBD had been affected.

Three substations: Bree, Braamfontein and Johnware substations were not switched back on after load shedding last night and would remain so until the Joint Command Team comprising the CoJ Emergency Services, Disaster Management and other CoJ and Provincial units have given the go-ahead.

“Bree substation is a few meters away from the area with the huge impact, and the suspicion is that its structural integrity may have been affected. Our team of engineers and technicians are on site doing assessments and tests on the network to get the extent of the impact on the electricity infrastructure,” the statement read.

A joint operations committee, with representatives from the South African Police Service, Disaster Management Services, and other key stakeholders, has been formed to investigate.

“It’s definitely under control. It’s not a ticking time bomb,” Brink said.