Fallen power lines touch the ground on Camino Diablo road in Lafayette, California, U.S., on Monday, Oct. 28, 2019.

Pacific Gas & Electric Co. power lines may have started two wildfires over the weekend in the San Francisco Bay Area, the utility said Monday, even though widespread blackouts were in place to prevent downed lines from starting fires during dangerously windy weather.

The fires described in PG&E reports to state regulators match blazes that destroyed a tennis club and forced evacuations in Lafayette, about 20 miles (32 kilometers) east of San Francisco.

The fires began in a section of town where PG&E had opted to keep the lights on. The sites were not designated as a high fire risk, the company said.

Powerful winds were driving multiple fires across California and forcing power shut-offs intended to prevent blazes. PG&E said a contractor working in Humboldt County died in a vehicle accident during the power shutoff Friday.

More than 900,000 power customers — an estimated 2.5 million people — were in the dark at the height of the latest planned blackout, nearly all of them in PG&E's territory in Northern and central California. By Monday evening a little less than half of those had their service back. But some 1.5 million people in 29 counties will be hit with more shut-offs starting Tuesday because another round of strong winds is expected, the utility said.

Southern California Edison had cut off power to 25,000 customers and warned that it was considering disconnecting about 350,000 more as Santa Ana winds return midweek.

PG&E is under severe financial pressure after its equipment was blamed for a series of destructive wildfires during the past three years. Its stock dropped 24% Monday to close at $3.80 and was down more than 50% since Thursday.

The company reported last week that a transmission tower may have caused a Sonoma County fire that has forced nearly 200,000 people to evacuate.