Towering wildfires burned out of control across Southern California for a third day on Tuesday as 500,000 people fled the San Diego area, and firefighters made a desperate stand to save a mountain town ringed by flames.

More than a dozen fires blazed from the horse country north of Los Angeles to the Mexican border 150 miles to the south, torching 1,500 houses and other buildings, blotting out the sun with smoke and raining ash on the streets.

Most of the destroyed homes were in the San Diego area, where three major wildfires burned unchecked and half a million people were ordered to leave in what may be the largest U.S. evacuation since Hurricane Katrina hit the Gulf Coast in 2005.

At least five deaths were reported, three of them elderly evacuees from the San Diego area, and more than three dozen others had been injured, including 18 firefighters.

As the firestorms raged into the evening, Gov. Arnold Schwarzenegger asked President George W. Bush to upgrade California's wildfires to a "major disaster," which would trigger federal help.

Bush already issued a declaration of emergency early Tuesday. But Schwarzenegger told him in a new letter that "this disaster is of such severity and magnitude that effective response is beyond the capability of the state and local governments."

Schwarzenegger said 68,000 homes, from cabins to luxury villas, were threatened statewide and 6,000 men and women were working the fire lines. More than 300,000 acres (120,000 hectares) have been blackened and the state government put economic losses in the hundreds of millions.

"We have had three things come together -- very dry areas, very hot weather and a lot of wind. This makes the perfect storm for fire," Schwarzenegger said at Lake Arrowhead, where blazes threatened two nearby mountain communities.

San Diego Mayor Jerry Sanders put the number of evacuees at half a million.

Bush planned to visit the fire-stricken area on Thursday.

TOWN SURROUNDED BY FIRE

Running Springs, a town of about 5,000 people nestled in the San Bernardino Mountains, was surrounded by fire by Tuesday afternoon as crews made a furious effort to save homes.

Firefighters in the Mexican border city of Tecate tried to control fires that sent up black smoke and covered houses and cars with gray ash. Fires also burned on the outskirts of the Mexican city of Tijuana, 20 miles from San Diego.

California power authorities issued a transmission emergency because downed power lines had left San Diego with only 60 percent of its usual supply of electricity.

The hot Santa Ana winds, which have fanned the flames as they blow in to Southern California from the desert, continued to gust up to 65 mph (105 kph) and high wind warnings remained in effect for most of the region until Wednesday afternoon.

Officials were hoping that easing winds and an accompanying rise in humidity would help them gain the upper hand against the wildfires.

San Diego officials said people were evacuating quickly. In the region's last major fire in 2003, 15 people died and 5,000 buildings were destroyed. But Erica Schmidt said friends in San Diego county ignored evacuation orders to safeguard their own homes.

"It bothers me to know my friends are still up there because they can't get out," Schmidt said.

Some 8,000 people, including senior citizens from nursing homes, went to the Qualcomm stadium, where the San Diego Chargers football team plays, or to the Del Mar Fairgrounds, famed for its horse racing track. Thousands of horses and family pets were also accommodated.

People taking shelter at Qualcomm called it well organized and clean, in contrast to the chaos at New Orleans' Superdome, which was used as a refuge after 2005's Hurricane Katrina.

On Tuesday afternoon, some San Diego evacuees were allowed to return to their communities.

George W. Bush California