(CNN)California's Bay Area Rapid Transit system says it is running "limited service" to the Oakland International Airport because of a power outage in Alameda County.
"Oakland Airport Connector service is running limited service due to a power outage. Shuttles will depart every 18 minutes," BART said in a 2:38 p.m. PST update.
Pacific Gas and Electric Company spokesperson Tamar Sarkissian tweeted that a "large outage" was impacting approximately 50,000 Oakland customers. By about 6:30 p.m. Sunday evening, the utility had restored power to about 20,000 customers, spokesperson JD Guidi said in a statement.
A transformer fire at a substation caused the outage, Pacific Gas and Electric told CNN in an email Sunday evening.
"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," Guidi said.
Some customers may remain without power for up to 12 hours as the utility works to replace the transformer, according to Guidi.
The Oakland Fire Department later tweeted that the transformer that had been "actively burning" had been extinguished.
"The fire at the substation located at 50th x Coliseum is now out," it said. "There is no Hazmat concern or evacuations necessary."
The outage impacted the Oakland International Airport for more than an hour Sunday afternoon, according to airport spokesperson Robert Bernardo.
The power at the airport went down at approximately 1 p.m. PST and was restored at 2:50 p.m. PST, Bernardo told CNN.