US President Donald Trump has approved a major disaster declaration for California as the state continued to fight wildfires that have killed more than 30 people and destroyed nearly 7,000 structures.

"I just approved an expedited request for a Major Disaster Declaration for the State of California," he wrote on Twitter on Monday evening. "Wanted to respond quickly in order to alleviate some of the incredible suffering going on. I am with you all the way. God Bless all of the victims and families."

Meanwhile, emergency teams searched on Monday for more than 200 people listed as missing in the deadliest Northern California wildfire on record, and officials voiced concerns the casualty toll will climb higher as a resurgence of fierce winds fanned the flames.

Taken together, the northern Camp Fire, the southern Woolsey Fire and a handful of smaller blazes in Southern California have displaced more than 224,000 people, CalFire said.

About 8,000 firefighters were battling the flames, backed by squadrons of water-dropping helicopters and airplane tankers, including crews from out of state.

Governor Jerry Brown, a Democrat, had asked Trump to declare a major disaster to bolster the emergency response and help residents recover.

Trump, a Republican who has often criticized California on various issues, blamed poor forest management for the infernos.

Brian Rice, president of the California Professional Firefighters, called Trump's statement "ill-timed" given the loss of life and search for missing people.

The deadly Camp Fire also ranked as California's most destructive in terms of property losses, having incinerated more than 6,700 homes and other buildings in the Sierra foothills of Butte County, about 175 miles north of San Francisco.

More than 15,000 more structures remained listed as threatened on Monday in an area so thick with smoke that visibility was reduced in some places to less than half a mile.

Most of the devastation and loss of life was in and around the town of Paradise, where flames reduced most of the buildings to ash and charred rubble on Thursday night, just hours after the blaze erupted. At least 29 fatalities have been confirmed so far, a tally that ranks as the most ever from a single Northern California wildfire.

Authorities reported two more people perished over the weekend in Woolsey Fire, which has destroyed 370 structures and displaced some 200,000 people in the mountains and foothills near Southern California's Malibu coast.

The remains of some of the Camp Fire victims were found in burned-out vehicles that were overrun by walls of fire as evacuees tried to flee by car in panic, only to be trapped in deadly knots of traffic gridlock on Thursday night.

A man who led a caravan of vehicles that was overcome by flames from a wildfire says he saw his friend die. Greg Woodcox told The Associated Press on Monday that he heard his friend scream as the heat blew out windows. Four other people in the vehicles died.

At least 228 people were listed as unaccounted for early on Monday, according to Butte County Sheriff Kory Honea.

Perilous winds that stoked the fire through drought-parched brush and chaparral abated on Sunday, giving firefighters a chance to gain some ground against the flames.

By Monday, they had managed to carve containment lines around 25 percent of the Camp Fire perimeter, an area encompassing 113,000 acres of scorched, smoldering terrain.

The Woolsey Fire has charred more than 91,000 acres and was 20 percent contained as of Monday, according to CalFire.

Winds of up to 40 mph were expected to continue in Southern California through Tuesday, heightening the risk of fresh blazes ignited by scattered embers.

Malibu resident Tony Haynes described how strong winds brought the fire through his neighborhood during the weekend, with the sky growing dark, saying there was so much smoke he put on his scuba-diving tank to breathe. Haynes said his home survived.

REUTERS-AP