LA fire
© Kevork Djansezian/Getty ImagesLos Angeles County firefighters Kevin Klar, right, and Eric Tucker, center, sat with homeowner Henrik Hairapetian as fire scorched the La Canada Flintridge foothills on Saturday
A wildfire raging in the mountains north of Los Angeles spread rapidly to the northwest and southeast Saturday night into Sunday, consuming thousands of acres of national forest land and threatening at least 10,000 homes in suburban and rural communities in the foothills, the National Forest Service said.

Fueled by high temperatures and low humidity, the fire has more than quadrupled in size since Friday, scorching more than 35,000 acres of underbrush, scrub oak and mature trees and destroying three dozen cabins inside the Angeles National Forest. Much of the area has been fire-free for 50 to 60 years, providing plenty of dead undergrowth to fuel the flames.

"It's a pretty ugly scene out there," Bruce Quintelier, a fire information officer for the United States Forest Service, said in a telephone interview. "It has got a lot to burn."

The so-called Station Fire, which began on Wednesday and threatens communication towers and an astronomical observatory, was the largest and most dangerous of several burning around southern and central California and in Yosemite National Park on Sunday.

The authorities ordered communities in Crown Valley, Soledad Canyon and Alison Canyon to evacuate as the Station Fire moved closer. The flames particularly threatened the community of Acton on the north side of the San Gabriel Range, where residents reported Saturday that ashes were falling from a black daytime sky, Mr. Quintelier said.

About 1,800 firefighters worked Saturday to fight the flames, both by dumping water from the air and by building fire breaks around the perimeter of the burn area. As of Saturday night, however, only 5 percent of the blaze had been contained. Thick smoke prevented some fire fighting planes from taking off on Saturday, and officials were hoping for better conditions on Sunday.

Almost 100 miles of fire break had yet to be built to keep the fire from spreading. In foothills communities, about 150 fire trucks stood ready as a precaution. "This fire is probably a week away from being fully contained," Mr. Quintelier said. "It's just a long marathon sort of job that lies ahead."

Temperatures, which have been in the triple-digits in some inland Los Angeles areas, were expected to be slightly lower on Sunday, somewhat easing conditions. But a significant change in the weather was not expected for several days. A saving grace for threatened communities, however, is that winds have remained low.

Four injuries have been reported. On Saturday, three people suffering from burns were evacuated from the Angeles forest, and on Friday one firefighter was treated for heat exhaustion and smoke inhalation, the National Forest Service said. Smoke lingered over much of Los Angeles county, and people with respiratory difficulties, children and the elderly in affected areas were urged to stay indoors.

Among the smaller fires, a 3.7-square-mile fire in the San Bernardino National Forest, southeast of Los Angeles in Riverside County, was 75 percent contained Sunday morning as it burned in steep, rocky terrain in Beeb Canyon. No structures were threatened.

To the north, in the state's coastal midsection, a 9.9-square mile fire threatening Pinnacles National Monument kept 100 homes under evacuation orders near the Monterey County town of Soledad. The blaze, 80 percent contained by Sunday, was started by agricultural fireworks used to scare animals away from crops, The Associated Press reported. The fire destroyed one home.

A state of emergency was declared Saturday for Mariposa County, where a nearly 4,300 acre fire burned in Yosemite National Park. The blaze was 50 percent contained as of Sunday morning, park officials said.