A massive power outage in San Francisco was caused by a fire at a PG&E substation, a PG&E official said at a press conference April 21.

“I’d like to extend our apologies to our customers,” said Barry Anderson, vice president of electric distribution for PG&E. “The outage was caused by a catastrophic failure in one of our circuit breakers. (The failure) caused a fire around the breaker insulation, and that’s what created the situation.”

At the time of the 2 p.m. press conference April 21, about 30,000 customers were still without power.

“We have checked with hospitals and trauma centers and there were no major injuries,” Mayor Ed Lee said. “All major arteries emanating to and from the city are now operational. Many of our officers are managing exits and entries.”

The outage started shortly after 9 a.m., and Lee said about 88,000 PG&E customers were affected.

The outage caused a BART station to shut down earlier in the day. Passengers couldn’t get off at the Montgomery BART station for about two hours, but the station opened again around 11:30 a.m.

The outage affected central and northern neighborhoods in the city including the Western Addition, Pacific Heights, Japantown, Polk Gulch, Russian Hill, the Marina, the Richmond, the Presidio, Laurel Heights, the Sunset, the financial district, Chinatown, North Beach and Fisherman’s Wharf.

San Francisco schools remained open, the San Francisco Unified School District said earlier in the day. Twenty-one school sites and one district office building were affected, the district said.

The San Francisco Fire Department scrambled to keep up with more than 100 calls for service in about two hours, with 20 different elevator rescues requested.