The number of people missing in one of California's deadliest wildfires has soared to more than 600 as rescuers found the remains of another seven victims.
Authorities said the list of missing people jumped from 300 to 631 on Thursday as investigators went back and reviewed emergency calls made when the so-called Camp Fire in northern California erupted on November 8.
"I want you to understand that the chaos we were dealing with was extraordinary" when the fire broke out, Butte County Sheriff Kory Honea said, in explaining the surge in the number of people missing.
The seven additional victims raised the death toll from the Camp Fire to 63.
At least three other people died in southern California in another blaze dubbed the Woolsey Fire, which engulfed parts of Malibu, destroying the homes of several celebrities.
President Donald Trump is set to visit the state on Saturday to meet with victims of the wildfires, the deadliest and most destructive in the state's history.
Many of the victims and the hundreds missing in the Camp Fire were elderly people who lived in the Butte County town of Paradise, in the foothills of the Sierra Nevada mountains. It is believed they were unable to flee the fast-moving blaze or were trapped in their cars as they attempted to escape.
Mr Honea said the number of those missing was likely to fluctuate as people call in to report loved ones unaccounted for or found alive.
"If you look at that list and see your name, or the name of a friend or loved one, please call to let us know," he said.
Investigators on Thursday collected DNA samples from relatives to help identify victims as hundreds of rescue personel and sniffer dogs worked to locate more victims.
Authorities said a wanted felon was killed inside the evacuation zone on Thursday following a high-speed chase with police. The man was wanted for a double homicide in 2014 and had been seen for three days camped out in his car.
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Virtually every home in Paradise, located 130 kilometres north of the state capital Sacramento, was destroyed by the fire, which was driven by high winds.
Body recovery teams are conducting a painstaking search of burned-out homes for human remains in the town and closely examining the many charred cars littering the roads.
The 63 deaths reported from the Camp Fire make it the deadliest wildfire in California's history, as the inferno also became the most destructive.
The California fire department said on Thursday that the Camp Fire had destroyed 56,655 hectares and was 40 per cent contained.
It said nearly 5,500 firefighters were battling the blaze and it did not expect it to be fully contained for another two weeks.
The Camp Fire has destroyed more than 8,650 single-family homes and 260 commercial buildings, the fire service said.
The Woolsey Fire has razed 39,660 hectares and has been 62 per cent contained. It is expected to be fully contained by Monday.
Authorities said cooler temperatures and calmer winds had brought welcome relief to fire crews.
A number of celebrities have lost their homes in Malibu as a result of the Woolsey inferno, including Pierce Brosnan, Miley Cyrus, Neil Young, Robin Thicke, Shannen Doherty and Gerard Butler.
California Governor Jerry Brown, Interior Secretary Ryan Zinke and Brock Long, head of the Federal Emergency Management Agency, toured the damage in Paradise on Wednesday.
"This is so devastating that I don't really have the words to describe it," Mr Brown said. "It looks like a war zone."
Authorities said it was unclear when residents would be allowed back into the town.
While the cause of the Camp Fire is still under investigation, a lawsuit has been filed against the local power company, PG&E, by fire victims claiming negligence by the utility.
The complaint alleged that the fire began on November 8 when a high voltage transmission line failed, igniting tinder-dry vegetation.
The utility was found to be responsible for several devastating fires in northern California last autumn that killed at least 15 people, and it faces billions of dollars in liability for the latest wildfires.