A wildfire in the mountains above Los Angeles has surged in every direction, going in a single day from a modest threat to a danger to some 10,000 homes.

The blaze nearly tripled in size in the heat on Saturday, leaving three people burned, destroying at least three homes and forcing the evacuation of 1,000 homes and an untold number of people.

A slight drop in temperatures and an influx of fire crews from around the state were expected to bring some relief on Sunday.

Mandatory evacuations were in effect for neighborhoods in Altadena, Glendale, Pasadena, La Crescenta and Big Tujunga Canyon.

The flames crept down the slopes of the San Gabriel Mountains despite mild winds blowing predominantly in the other direction.

``Today what happened is what I call the perfect storm of fuels, weather, and topography coming together,'' said Captain Mike Dietrich, the incident commander for the U.S. Forest Service. ``Essentially the fire burned at will; it went where it wanted to when it wanted to.''

Dietrich said he had never seen a fire grow so quickly without powerful Santa Ana winds to push it.

At least three homes deep in the Angeles National Forest were destroyed, and firefighters were searching for others, Dietrich said.

Evacuation centres were set up at two high schools and an elementary school in the area.

The fire was the largest and most dangerous of several burning around southern and central California and in Yosemite National Park.

More than 31 square miles (80 square kilometers) of dry forest was scorched by the fire. It was only 5 percent contained.

At least three people were burned in the evacuation areas and airlifted to local hospitals, Dietrich said. He had no further details on their injuries.

Air crews waged a fierce battle against the southeast corner of the fire, burning dangerously close to canyon homes.

The fire was burning in steep wooded hills next to NASA's Jet Propulsion Laboratory in northern Pasadena.

In La Vina, a gated community of luxury homes in the Altadena area, a small group of residents stood at the end of a cul-de-sac on the lip of a canyon and watched aircraft battle flames trying to cross the ridge on the far side.

At one point, the flying circus of relatively small propellor-driven tankers gave way to the sight of a giant DC-10 jumbo jet unleashing a rain of red retardant.

``We see a drop, we give a big cheer,'' said Gary Blackwood, who works on telescope technology at the Jet Propulsion Laboratory.

``We've watched it now for two days hop one ridge at a time and now it's like we're the next ridge.''

A major goal was to keep the fire from spreading up Mount Wilson, where many of the region's broadcast and communications antennas and the historic Mount Wilson Observatory are located, officials said.

A number of other smaller fires were also burning across the region.

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