The Allandale substation near Tembisa in Ekurhuleni which caught fire on Wednesday, causing power outages in the area, is back online.

"We can confirm that suburbs affected by transformer fire are fully restored. They include Rabie Ridge 1,2,4 and 5, Mayibuye, Commercia extension nine and & Austin view. Allandale substation power is 100% restored. We thank the hardworking technicians from City Power and Eskom!" City Power tweeted late on Wednesday evening.

Eskom spokesperson Khulu Phasiwe earlier said the cause of the fire was unknown.

Meanwhile, stage 4 load-shedding will continue on Human Rights Day from 9am to 11pm because of a capacity shortage.

"Load-shedding is a highly controlled process‚ implemented to protect the system and to prevent a total collapse of the system or a national blackout‚" Eskom tweeted on Wednesday evening.