Twenty-one thousand San Francisco customers remain without power on Sunday morning as PG&E crews continue to work to restore electricity after a now nearly day-long outage. 

The issue appeared to originate from a PG&E substation at 8th and Mission streets, Supervisor Matt Dorsey said on social media. At around 3:15 p.m. Saturday, the San Francisco Fire Department reported they were responding to a fire at the location. Dorsey, who represents the South of Market district, said the same substation was responsible for a blackout on Dec. 21, 2003, affecting about 120,000 customers at the time.

“The damage from the fire in our substation was significant and extensive, and the repairs and safe restoration will be complex,” PG&E said in a news release early Sunday morning.

By 11:30 p.m. Saturday, PG&E had restored power to about 100,000 customers, leaving 21,000 still in the dark as of Sunday. “At this time, we are unable to provide a precise timeframe for full restoration but will provide additional detail and information as our assessment and repair efforts continue,” the utility company said in a statement. The PG&E outage map shows the biggest pockets that haven’t had their power yet restored are primarily between the Presidio and Golden Gate Park, with another pocket downtown around the 8th and Mission substation.

“This is a very complex work plan and will require the highest amount of safety focus to ensure safe work actions,” PG&E said in a statement. As of 11 a.m. Sunday, PG&E still did not have an updated timeline for when power will be restored to the remaining 21,000 customers. 

At the height of the outages, approximately 130,000 San Francisco customers were without power, or approximately 30% of the city. Impacted areas included the Richmond, Sunset, Haight Ashbury, Hayes Valley, Forest Hill, all of Golden Gate Park and the Presidio and parts of downtown and South of Market. Outages were reported as early as about 9:40 a.m. in some parts of the city. 

The outage created driving chaos on the streets of San Francisco as traffic lights were down throughout the city. Waymo’s self-driving cars were put on pause by the company after the autonomous vehicles were baffled by the lack of traffic lights, getting stuck at intersections and causing traffic jams.

Bay City News Service contributed to this report.