At least 42 people were confirmed dead in the wildfire that turned the Northern California town of Paradise and outlying areas into hell on earth, making it the deadliest blaze in state history.

The death toll made this blaze the deadliest single fire on record, surpassing the toll from a 1933 blaze in Griffith Park in Los Angeles that killed 29. A series of wildfires in Northern California's wine country last fall killed 44 people and destroyed more than 5,000 homes.

The dead were found in burned-out cars, in the smouldering ruins of their homes, or next to their vehicles, apparently overcome by smoke and flames before they could jump in behind the wheel and escape. In some cases, there were only charred fragments of bone, so small that coroner's investigators used a wire basket to sift and sort them.

The search for bodies continued on Monday. Authorities said they were bringing in cadaver dogs, two portable morgue units from the military and an additional 160 search and rescue personnel to help find human remains

“This is an unprecedented event,” Butte County Sheriff Kory Honea told an evening news conference. “If you've been up there, you also know the magnitude of the scene we're dealing with. I want to recover as many remains as we possibly can, as soon as we can. Because I know the toll it takes on loved ones.”

Officials said they did not know how many people were missing four days after the fire swept over the town of 27,000 and practically wiped it off the map with flames so fierce that authorities brought in a mobile DNA lab and forensic anthropologists to help identify the dead.

Meanwhile, a landowner near where the blaze began, Betsy Ann Cowley, said she got an email from Pacific Gas & Electric Co. the day before the fire last week telling her that crews needed to come onto her property because the utility's power lines were causing sparks. PG&E had no comment on the email, and state officials said the cause of the inferno was under investigation.

As the search for victims dragged on, friends and relatives of the missing called hospitals, police, shelters and the coroner's office in hopes of learning what became of their loved ones. Paradise was a popular retirement community, and about a quarter of the population was over 65.

Tad Teays awaited word on his 90-year-old dementia-stricken mother. Darlina Duarte was desperate for information about her half brother, a diabetic who was largely housebound because he had lost his legs.

Barbara Hall tried in vain to find out whether her aunt and the woman's husband, who are in their 80s and 90s, made it out alive from their retirement community.

“Did they make it in their car? Did they get away? Did their car go over the edge of a mountain somewhere? I just don't know,” said Hall, adding that the couple had only a landline and calls were not going through to it.

Megan James, of Newfoundland, Canada, searched via Twitter from the other side of the continent for information about her aunt and uncle, whose house in Paradise burned down and whose vehicles were still there.

On Monday, she asked on Twitter for someone to take over the posts, saying she is “so emotionally and mentally exhausted".

“I need to sleep and cry,” James added. “Just PRAY. Please.”

The blaze was part of an outbreak of wildfires on both ends of the state. Together, they were blamed for 44 deaths, including two in celebrity-studded Malibu in Southern California , where firefighters appeared to be gaining ground against a roughly 370-square-kilometres blaze that destroyed at least 370 structures, with hundreds more feared lost.

Some of the thousands of people forced from their homes by the blaze were allowed to return, and authorities reopened US 101, a major freeway through the fire zone in Los Angeles and Ventura counties.

Malibu celebrities and mobile-home dwellers in nearby mountains were slowly learning whether their homes had been spared or reduced to ash.

All told, more than 8,000 firefighters statewide were battling wildfires that destroyed more than 7,000 structures and scorched more than 840 square kilometres, the flames feeding on dry brush and driven by blowtorch winds.

In Northern California, fire crews still fighting the blaze that obliterated Paradise contended with wind gusts up to 40 mph overnight, the flames jumping 300 feet across Lake Oroville. The fire had grown to 303 square kilometres and was 25 per cent contained, authorities said.

Winds were expected to weaken on Monday night.

Greg Woodcox, who led a caravan of vehicles that was overcome by flames, said he heard screams and watched a friend die as the heat blew out the vehicle's windows. Four other people also died.

The 58-year-old told the San Francisco Chronicle he was in a Jeep ahead of the other vehicles and ran when the flames overtook them. He followed a fox down a steep embankment and survived by submerging himself in a stream for nearly an hour.

But there were tiny signs of some sense of order returning to Paradise and anonymous gestures meant to rally the spirits of firefighters who have worked in a burned-over wasteland for days.

Large American flags stuck into the ground lined both sides of the road at the town limits, and temporary stop signs appeared overnight at major intersections. Downed power lines that had blocked roads were cut away, and crews took down burned trees with chain saws.