A transformer failure is thought to be responsible for an explosion and major fire at an electrical substation in Adelaide's inner west that cut power to about 6000 properties.
About 40 firefighters battled the blaze at suburban Thebarton on Wednesday, with large plumes of black smoke prompting authorities to urge residents to stay indoors.
SA Power Networks said it would need to wait until it was safe to enter the site before assessing the damage.
"No one was working at the substation at the time of the event and, thankfully, there have not been any reports of injuries," spokesman Paul Roberts said.
"While there was a lot of smoke and flames, the damage has been contained to the substation site."
Power was restored to all customers by 4.45pm, but the Metropolitan Fire Service said crews would remain on the scene for several hours as they continued to monitor the transformer with thermal imaging cameras amid concerns oil inside could re-ignite.