A pair of widespread power outages left thousands of customers without electricity Friday afternoon across San Francisco, according to Pacific Gas and Electric Co., with some traffic signals also knocked offline.

The outages came as San Francisco experienced record-breaking heat. Downtown temperatures reached 90 degrees Friday, surpassing the previous March record of 87 degrees set in 2005, according to the National Weather Service.

The number of affected PG&E customers fluctuated throughout the afternoon as crews worked to restore service. The utility reported that more than 7,000 customers were without power.

“A large, unplanned power outage is impacting multiple neighborhoods and moving throughout the city,” San Francisco’s Department of Emergency Management said around 3:15 p.m. in a social media post.

In a statement issued about two hours later, PG&E said an electrical equipment failure in an underground vault at 18th and Guerrero streets was a cause of the outages.

“Crews are on site working to safely restore power as quickly as possible,” the utility said.

PG&E added that it had restored service to about 11,000 customers and that roughly 3,100 customers remained without power.

A city employee monitoring the outage said PG&E’s public updates may have caused confusion about the scope of the disruptions. According to the employee, what appeared to be a single outage affecting roughly 14,000 customers was in fact a sequence of separate outages impacting different, partially overlapping groups of customers.

PG&E has not publicly clarified that distinction, nor has it released a cause for the outages.

The outages affected multiple neighborhoods on the city’s west side, including parts of the Sunset District, Lower Haight, Castro and Cole Valley.

Several businesses said they were impacted. 

City officials have raised concerns in recent months about repeated outages and reliability issues. After a major December blackout left roughly one-third of San Francisco without power, local leaders called for a state investigation into PG&E’s service.

The California Public Utilities Commission has said its review of that incident was ongoing.