LOS ANGELES - FIRES raged across California for a fourth day on Sunday as investigators began sifting through the smoldering aftermath of infernos that have destroyed more than 800 homes and forced thousands to flee.

Around 800 residences - ranging from multi-million-dollar mansions to modest prefabricated mobile homes - have been razed by a series of wind-whipped fires that have erupted through the region since Thursday.

At least 50,000 evacuation orders have been issued and nearly 8,900 hectares have been destroyed in the blazes, which have stretched from Santa Barbara to south-east of Los Angeles.

A fire that struck in Los Angeles late on Friday was described as one of the worst to hit the city in nearly half a century but so far only 11 injuries have been reported across the entire region.

Urban search and rescue teams including cadaver dogs were Sunday sent into the ground zero of the Los Angeles fire, a mobile home park in the northern suburb of Sylmar where more than 500 residences were incinerated.

Los Angeles Police Department deputy chief Michael Moore told a press that approximately 30 per cent of the devastated mobile home park had been searched on Sunday and no human remains had been found.

'At this point we have no missing persons, no reported missing persons or no evidence to tell us that there is loss of life', Mr Moore said. 'It is an exceedingly difficult task. There's still much work ahead of us.'

Los Angeles fire officials meanwhile said progress had been made overnight Saturday in tackling the 3,844-hectare fire, with 30-per cent containment reached after a lull in fierce local winds.

The cause of the fire remains unknown.

California Governor Arnold Schwarzenegger, who has declared a state of emergency in the fire affected areas, told a briefing on Sunday authorities were dealing with a 'perfect storm'.

'With all these fires all over, this is usually what happens at this time of the year, when we have the perfect storm, which means basically we have high winds, high temperatures and very very dry', Mr Schwarzenegger said.

Los Angeles Mayor Antonio Villaraigosa said the destruction was unprecedented. 'What you see is devastation that I've never seen before', he said. 'Our hearts are out with all of the people who lost their home'.

A total of around 3,700 firefighters, using helicopters, bulldozers and engines, were battling fires across the state.

Meanwhile, the focus of firefighting efforts had shifted Sunday to Orange County, south of Los Angeles, where a 4,230-hectare complex of fires near Yorba Linda and Corona was ablaze.

The fire had destroyed at least 104 residences and eventually prompted as many as 40,000 evacuations in three counties.

Fire officials said they had struggled to keep pace with the fires as they swept through tinder-dry brush and chapparal.

'We just started losing homes. We didn't have enough units', said Mr Mickey Hansen, a safety officer with the Orange County Fire Authority. 'There were just so many fires. There wasn't enough (resources) to go around'.

Thick smoke from the Orange County fires had settled over Los Angeles on Sunday, blotting out the downtown skyline as well as famous landmarks such as the city's iconic Hollywood sign.

Meanwhile, hundreds of firefighters were making steady progress against the fire which tore through the millionaires' playground of Montecito after erupting on Thursday.

Some 210 residences had been gutted by the fire, which has burned around 785 hectares and was 75-per cent contained.

California is frequently hit by scorching wildfires due to its dry climate, Santa Ana winds and recent housing booms which have seen housing spread rapidly into rural and densely forested areas.

Only just over a year ago California suffered devastation from wildfires among the worst in its history that left eight people dead, gutted 2,000 homes, displaced 640,000 people and caused one billion US dollars (S$1.52 billion) in damage.

In June and July this year, a series of about 2,000 fires raged across the state, scorching some 364,230 hectares of land. -- AFP