Johannesburg - City Power on Tuesday said it was currently investigating the cause of the fire at a switching substation at Vasco Da Gama in Alexandra township in Johannesburg.
City Power spokesperson Isaac Mangena, said the fire started around lunch time on Tuesday razing the substation to the ground.
The fire plunged over half of Alexandra, between 2nd Avenue and 18th Avenue, into darkness.
"By this afternoon some of the cables were still smouldering making it difficult for technicians to start the work. The repair work will involve putting in new infrastructure including RMUs and cables that were totally destroyed during the fire.
"The repairs will take at least 48 hours after which time power will only be restored," said Mangena.
"It is suspected that vandalism could be the cause of the fire after the gates leading into the substation were found to have been broken into, but that will form part of the investigation."
He said the substation was over 50 years old and was the same one that caught fire almost two weeks ago leaving half of Alexandra without power for two days.
"The process was already underway to build a new one as part of upgrading electricity infrastructure across Alexandra township. A total of R16 million has been budgeted this financial year for the upgrade of this substation," said Mangena.
"We apologise to the customers for the inconvenience caused by this unfortunate incident."
City Power chief executive officer Lerato Setshedi appealed to communities to protect their infrastructure against vandalism and theft.