About 80 shacks caught fire in Alexandra, Johannesburg on Tuesday afternoon.
According to City Power spokesperson Isaac Mangena, a pylon and overhead line, carrying about 88 kilovolts of electricity, fell on the shacks.
Mangena said the line could cause injuries and even death. Several areas are expected to be without electricity.
"As of now, we don't know the cause of this. We are also not sure if there are casualties. We have dispatched a team to the area to investigate," said Mangena.
Johannesburg Emergency Management Services spokesperson Nana Radebe said they received the call at about 13:30.
"[There were] about 20 shacks on fire," Radebe said at the time.
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"For now, we cannot confirm the exact number of shacks. We will get the clear number after we are done with the firefighting," Radebe added.
At about 17:00, Radebe said 80 shacks burnt down.
She added that Disaster Management was on scene to establish the number of affected shacks.
"By the way we see it now, it is plus minus 80 shacks," she said.
The fire has been contained but firefighters were still busy because they wanted to ensure that it did not reignite, Radebe added.