© AP Photo/Jason RedmondA firefighter looks on as they battle the Station fire burning in the Angeles National Forest northeast of downtown Los Angeles on Firday, Aug. 28, 2009. The Los Angles Sheriff's Department says a voluntary evacuation is being urged for nearly 900 homes in the La Canada Flintridge area.
A growing wildfire sending massive billows of smoke into the sky north of Los Angeles nearly tripled in size Saturday, knocking out power to homes and prompting evacuations in a number of mountain communities.

Mandatory evacuations were extended Saturday into neighborhoods in the canyons on the northwestern edge of Altadena and Glendale, Forest Service spokeswoman Rachel Mailo said. It was unclear how many residents were ordered to leave.

The flames burned increasingly lower down the slopes of the San Gabriel Mountains, threatening more than 2,000 homes in the La Canada Flintridge area. Fire burned right up to houses, but no structures were destroyed. At least 150 homes were under mandatory evacuation orders.

An evacuation center was set up at La Canada High School and Jackson Elementary School in Altadena.

Flames knocked out power to at least 164 residences in La Canada Flintridge Saturday afternoon, according to Southern California Edison. Repair crews were ordered to stay out of the area because of fire danger.

More than 31 square miles of dry forest was scorched by the fire, which continued to move out in all directions, the most active flanks to the north, deeper into the forest, and east, Mailo said. The blaze was only 5 percent contained.

Water-dropping helicopters made runs over the burning hillsides but the amount of smoke was hampering air operations in some areas.

"It's difficult for water-dropping aircraft to get in there, but they're still trying," Forest Service spokeswoman Jessica Luna said.

The fire was burning in hills adjacent to NASA's Jet Propulsion Laboratory in northern Pasadena. Nearby, Dawn James, 39, a physical therapist, and friend Leah Evans, 39, watched flames roil on the mountainsides from an equestrian park where they had brought two horses from their stables. James lives in the area and her husband stayed up at the house while she watched the horses.

"We always knew it could come. We knew it was a possibility," James said.

Evans said she watched the flames spread as she spent the night in her pickup truck near her horses.

"Through the night, you kind of watch it diminish, and then flare up," said Evans. "It's just amazing to watch, kind of unbelievable."

Dry conditions and triple-digit temperatures were expected all day Saturday, but crews were hopeful that winds would remain light.

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.

Hundreds of residents were packed and ready to move on a moment's notice.

"We're boxed up and ready to go," said La Canada Flintridge resident Steve Buntich, watching helicopters line up to siphon water from a golf course reservoir. He said his wife and children had moved to a friend's house for several hours, but had since returned home.

A thick layer of smoke hovered over the Los Angeles Basin and San Fernando Valley, and officials issued a smoke advisory for communities near the fire. Residents were urged to avoid exertion and seek air-conditioned shelter.

A second fire in the Angeles National Forest was burning several miles to the east in a canyon above the city of Azusa. The 3.4-square-mile blaze, which started Tuesday afternoon, was 85 percent contained Saturday. No homes were threatened, and full containment was expected by Monday.

A wildfire on the Palos Verdes Peninsula on the south Los Angeles County coast was 100 percent contained Saturday afternoon, according to county fire officials. As many as 1,500 people were forced to flee at the height of the fire Thursday night. Six homes received minor exterior damage, but the only structures destroyed were an outbuilding and gazebo. No injuries were reported.

Southeast of Los Angeles in Riverside County, a 3 1/2-square-mile fire in a rural area of the San Bernardino National Forest was 10 percent contained. Crews aided by aircraft were working to build a line around the fire, which was burning in steep, rocky terrain in Beeb Canyon, according to Forest Service spokeswoman Norma Bailey. No structures were threatened. Temperatures were expected to top 100 degrees in the region, but winds remained light.

To the north, in the state's coastal midsection, a 9.4-square-mile fire threatening Pinnacles National Monument kept 100 homes under evacuation orders near the Monterey County town of Soledad. The blaze, 60 percent contained, was started by agricultural fireworks used to scare animals away from crops. The fire destroyed one home.

In the southern part of Monterey County, firefighters had 100 percent containment of a 5 1/4-square-mile fire that had threatened 20 ranch homes.

Gov. Arnold Schwarzenegger declared a state of emergency Friday in Los Angeles and Monterey counties.

"It's fire season, clearly," he said. "There's tremendous amount of heat all over the state."

A state of emergency was declared Saturday for Mariposa County, where a nearly 4.1-square-mile fire burned in Yosemite National Park. The blaze was 15 percent contained, said park spokesman Scott Gediman. No structures were threatened.

Park officials closed a campground and a portion of Highway 120, anticipating that the fire would spread north toward Tioga Road, the highest elevation route through the Sierra. The number of firefighters was expected to double over the weekend to 1,000.

The Mariposa County Sheriff's Office ordered guests and staff at the Yosemite View Lodge, just outside the park's western gate, to evacuate Friday due to the fire. People without lodging were offered beds in a shelter in Mariposa staffed by the Red Cross.