The outage happened around 8am after a fire in City Power’s underground tunnels at Ntemi Piliso Street tripped two main lines to Central and Selby substation.
The cause of the fire is being investigated.
City Power senior managers and engineers met on site to draw up recovery and restoration plans and to assess alternative power supplies.
City Power said its teams were still unable to go into the tunnels in the afternoon because of safety concerns. It said work underground will start once the tunnels are declared safe.
By early Monday afternoon, emergency medical services (EMS) teams were busy trying to suck out the smoke from underground. They were unable to pinpoint the location of the fire within the affected 3km stretch of the tunnel.
“City Power technicians will not be able to go underground today. We may be able to on Tuesday afternoon, depending on an all-clear from the emergency and environmental services.
“The air quality and structural integrity will also be cleared before technicians can go down,” City Power said.
City Power said the fire affected power supply to most of the Johannesburg CBD, Booysens and Selby.
Environmental infrastructure services department MMC Michael Sun visited the site with City Power managers to assess the situation and monitor the recovery plans.
City Power said it anticipated that rush hour traffic on Tuesday morning will be affected as traffic lights in the CBD are not working