Dangerously high winds were expected to return to Los Angeles, jeopardising efforts to extinguish two massive wildfires that have levelled whole neighbourhoods, destroyed thousands of buildings and claimed the lives of at least two dozen people.

Dry Santa Ana winds of up to 80 to 112 kph were forecast to resume on Monday and persist through Wednesday, according to the National Weather Service, which issued a "particularly dangerous situation" red flag warning, the agency's most serious fire warning.

Fire crews were able to keep the fires from spreading overnight and are preparing for increased winds in the days ahead, officials said at a press conference on Monday morning.

"We are not in the clear," Los Angeles City Fire Chief Kristin Crowley said. "We must not let our guard down, as we have right now extreme fire behaviour."

Officials said the state was pre-positioning firefighting crews in vulnerable areas, including around the Palisades and Eaton fires, the two largest blazes burning on either side of Los Angeles. More than 8,500 firefighting personnel are assigned to those two fires.

Los Angeles County Fire Chief Anthony Marrone said firefighters were "absolutely better prepared" for extreme winds this week, after the fires grew rapidly last week following similar dire warnings from forecasters.

There are more personnel on the ground and additional firefighting aircraft in the air now, he said, though he acknowledged that nothing was guaranteed.

"We're never sure that we're going to be able to catch the next fire and keep it small," he said. "They said 70-mile-an-hour winds. It's going to be very difficult to contain that fire."

At least 24 people have died in the fires that began last Tuesday, and more than 150,000 residents have been forced to flee their homes. More than two dozen people are reported missing, authorities said.

Deputies are finding human remains every day as they search through the burned-out parts of Altadena, where the Eaton fire first ignited, Los Angeles County Sheriff Robert Luna said.

"It is a very grim task," Luna said, adding that he expected the confirmed death toll to rise in the days ahead.

The blazes have reduced entire neighbourhoods to smouldering ruins, leaving an apocalyptic landscape. California Governor Gavin Newsom has said the firestorm could rank as the most devastating natural disaster in US history. Private forecaster AccuWeather has estimated the damage and economic loss at US$135 billion to US$150 billion.

High winds threaten progress

The return of high winds threatens the hard-won progress that crews have made in containing the fires.

Over the weekend, aerial and land-based firefighters managed to stop the Palisades Fire as it encroached on the upscale Brentwood section and advanced toward the populous San Fernando Valley in the north.

That fire on the western side of the metropolis has consumed 96 sq km and stood at 14 per cent contained, a figure representing the percentage of the fire's perimeter that firefighters have under control.

City on alert

In anticipation of high winds returning on Monday, officials have warned the entire Los Angeles County population of nearly 10 million to be ready to evacuate.

As of Monday morning, more than 92,000 people in Los Angeles County were under an order to evacuate - down from a previous high of more than 150,000 - while another 89,000 faced evacuation warnings.

Active duty military personnel are ready to support the firefighting effort. FEMA Administrator Deanne Criswell told MSNBC on Monday that residents who are out of harm's way can begin applying for federal assistance, and that agency staffers are going to local shelters to help people get aid.

Firefighters from seven states, Canada and Mexico have already converged on the Los Angeles area to help fire departments from around the state.

In Altadena on the edge of the Eaton Fire, Tristin Perez said he never left his home, defying police orders to evacuate as the fire raced down the hillside.

Instead, Perez insisted on trying to save his property and his neighbours' homes.

"Your front yard is on fire, palm trees lit up - it looked like something out of a movie," Perez told Reuters in an interview in his driveway. "I did everything I could to stop the line and save my house, help save their houses."