Around 4am local time on Monday, just over 8,500 customers were impacted by the outage, according to PG&E. The company said it hoped to have power restored to its customers by noon.
At its height, the outage took out power for more than 50,000 customers.
The Oakland International Airport was among the sites that went dark after the fire. It reported power loss around 1pm on Sunday. Despite the outage the airport was able to maintain some operations, with a single security screening lane in Terminal 1 and two operating in Terminal 2.
TSA lines in the airport stopped during the initial outage, but began moving again by 3pm PST on Sunday.
The airport's power was restored a little more than an hour later.
City of Alameda officials reported that a pair of drawbridges were stuck in the up position during the outage. Drivers were advised to adjust their routes to avoid the crossing closures, according to KRON4.
BART officials said its Oakland Airport Connector route was forced to operate on limited service during the power outage.
By Sunday evening the company had restored power to about 20,000 customers, but noted at the time it could take up to 12 hours for its remaining affected customers to regain power.
The fire was extinguished at the substation around 4.30pm on Sunday, firefighters told KRON4.
“The cause of the outage is a transformer fire within the substation, and we are working closely with fire officials to make the situation safe. We will provide more information on the timing of restoration once we have those details,” PG&E spokesperson JD Guidi said in a statement to CNN.
PG&E issued a statement after the outage.
“The safety of our customers and employees is our most important responsibility. We are aware of the large outage in the Oakland area impacting approximately 50,000 customers,” the company said in the statement. “We are currently investigating the details, and will provide more information on the timing of restoration once we have more information.”