A fast-moving wildfire in northern California was sparked seven minutes after a nearby power line was damaged, according to a local power company.
Pacific Gas & Electric (PG&E) said damage had been reported at a high voltage tower near where the Kincade Fire started on Wednesday.
About 50,000 people have been evacuated from their homes in the state by wildfires driven by powerful winds.
A state of emergency has been declared in Los Angeles and Sonoma counties.
The deadliest wildfire in the state's history - which killed 85 people in northern California in 2018 - was caused by PG&E power lines.
Commenting on the latest fire, Governor Gavin Newsom said in a news conference on Friday that the company "simply did not do their job".
He condemned "years and years of greed, years and years of mismanagement in the utilities".
The company said it had not yet determined if the power glitch had sparked the Kincade Fire.
"We still, at this point, do not know what exactly happened," PG&E chief executive Bill Johnson told the Washington Post.
The utility said it had turned off power nearby over concerns that high winds could spark blazes, but the lines were still working when the fire ignited.
About 2,000 residents have been evacuated. At least 21 homes have been destroyed in the blaze, California fire officials said on Friday.
The wildfires are expected to worsen in southern California over the weekend as gusty winds continue.
California is still recovering from wildfires last year that killed about 100 people.
Where are the major fires?
The Kincade Fire, which started on Wednesday, has burned through 21,900 acres (8,800 hectares) of land in Sonoma County - one of California's best-known wine regions.
More than 1,300 firefighters are tackling the blaze, which remains uncontained.
There are a number of other major fires:
- The Tick Fire in Los Angeles County has burned at least 5,000 acres in the Santa Clarita region
- The Old Water Fire in San Bernardino County has burned 95 acres, shutting off a major highway
- The Cabrillo Fire in San Mateo County, south of the town of Pescadero, has burnt about 95 acres
- The Sawday Fire in San Diego County, which began on Friday, has burned 70 acres, some 40 miles northeast of San Diego
- The ongoing Saddle Ridge Fire in Los Angeles County has burned 8,700 acres over the last 14 days
What's caused the wildfires?
According to a report filed to the California Public Utilities Commission on Thursday, a "broken jumper" - which connects power lines to towers - was discovered at 21:20 local time on Wednesday.
The fire began at 21:27, according to the California Department of Forestry and Fire Protection.
The news sent share prices of PG&E tumbling on Friday, as investors feared the company might be held responsible for the Kincade Fire.
The company is already seeking bankruptcy protection as it faces lawsuits over last year's deadly Camp Fire. It was found to have been sparked by aging equipment owned by PG&E.
It spawned billions of dollars in liability claims against the company.
High winds appear to have spread the fires - gusts of up to 70mph (112km/h) have swept much of the state.
California is affected by Santa Ana winds, which are known for being dry and gusty, exacerbating wildfires.
Who is affected?
On Thursday morning PG&E shut off power in 15 California counties to prevent accidental fires, affecting about 180,000 homes.
Power was restored to most customers on Thursday night. But officials warn of more outages over the weekend in regions experiencing high winds and dry heat.
Schools in the Los Angeles Unified School District remained closed on Friday because of air quality and safety concerns.