WORKING AT CAPACITY: A Department of Forestry helicopter goes close to wildfire flames to make a water drop over the Del Dios neighbourhood of Escondido, California. Officials say resources have been stretched to the limits. -- PHOTO: AP

The evacuation was the largest in the state's history, and America's biggest since Hurricane Katrina, while state officials said the fires were the worst California had seen.

Some 1,300 homes have been lost in San Diego county, the most critical area, and an official estimated damage would exceed US$1 billion (S$1.47 billion).

President George W. Bush said he has signed a 'major disaster' declaration for Southern California and will head there today 'to make sure that our efforts are coordinated'.

At least five people have been killed and 45 hurt so far.

Governor Arnold Schwarzenegger said: 'We've had three things come together - very dry areas, very hot weather and then a lot of wind.

'And so this makes the perfect storm for a fire.'

Much of California has experienced record low rainfall and high temperatures this year, creating ideal conditions for fires which have been spread quickly by powerful desert winds.

Around 8,000 firefighters, including 2,600 prison inmates trained to tackle fires, supported by 90 firefighting aircraft, battled 18 blazes in seven counties yesterday.

But Orange County Fire Chief Chip Prather said the number of fires had stretched resources to breaking point: 'The bottom line is there are not enough air assets, not enough helicopters, not enough air tankers.'

Another 36,000 buildings are threatened,while Japanese tech firms Sony and Kyocera have been forced to close production facilities in the San Diego area.

The state's Office of Emergency Services said 13,570 people were in shelters.

AGENCE FRANCE-PRESSE, BLOOMBERG, REUTERS