Hundreds of firefighters struggled in erratic wind and rugged terrain Wednesday to save centuries-old giant sequoias from an out-of-control forest fire. Investigators, meanwhile, arrested a woman whose campfire may have started the blaze.

The wildfire blackened more than 50,000 acres, half of that inside Giant Sequoia National Monument, in a region that has had little or no rain since spring.

Peri Van Brunt, 45, was arrested at her home Wednesday and was being held on federal felony charges of unlawfully causing a fire, authorities said.

Van Brunt was tracked down from witness descriptions after she allegedly went into a store at the Roads End Lodge on Sunday saying her campfire had blown out of control, according to Forest Service officer Brian Adams.

"She ran in the store and said, 'Help, I started a fire,'" Adams said.

Van Brunt allegedly then fled with her dog as 30 mph winds blew the campfire into a conflagration. Minutes later, everyone else at the small lodge fled and the entire place burned down, leaving only the chimney.

Flames got to within two miles of a grove of sequoias called the Trail of 100 Giants, and within a mile of the Packsaddle Grove, which contains a tree with the fourth-largest circumference of any sequoia. Firefighters and forestry officials worried that the wind might push the blaze even closer to those and other stands of the mighty redwoods.

The monument's deep canyons and mountain ridges contribute to erratic winds.

"It's burning in every direction," forester Lewis Jump said. "It's the worst in the afternoon. The hot canyon winds are coming up and creating quite a bit of turbulence. That's what's pushing the fire."

More than 1,000 firefighters and 12 air tankers battled the blaze. The Forest Service called in six of the nation's elite Hotshot firefighting crews to help protect the trees. The trees in the Trail of 100 Giants are up to 1,500 years old and 220 feet tall, with trunks up to 20 feet across.

The fire began in the area of Johnsondale, a hamlet about 130 miles north of Los Angeles.

Fire permits have been required in the area because of the extremely dry conditions. Ranger Judy Schutza said Van Brunt did not have one.

"We understand that she's being cooperative and they are looking at the case being accidental rather than arson," said Jim Paxon, spokesman for a national team of elite firefighters called in to manage the blaze.

Van Brunt was being held Wednesday night at the Lerdo Pre-Trial Detention Facility north of Bakersfield, said Mary Buchanan, a jail clerk. She was to be arraigned Thursday in federal court in Fresno, Paxon said.

More than 1,000 residents, campers and other vacationers fled the area because of the fire. At least 10 structures burned and about 200 homes were threatened.

Elsewhere in the West:

— An 1,800-acre fire in California's Kern County was fully contained Wednesday after burning about 40 structures near Lake Isabella. Youths playing with matches are believed to have started it.

— Lightning during the night in Oregon started new fires in the Cascade Range and the high desert, forcing the evacuation of 60 campers and adults from a church camp outside Sisters.

— Dozens of people crowded into a memorial service for two pilots who died in an air tanker crash last week while working on a fire near Rocky Mountain National Park in Colorado.

About 250 firefighters who had been assigned to the 4,400-acre wildfire were sent elsewhere Wednesday and officials expected the blaze to be fully contained by Saturday. All residents evacuated from the area were allowed to return.

— In Washington, a 28,000-acre fire on the north shore of Lake Chelan was 35 percent contained Wednesday, but hot, dry weather was forecast and evacuation notices remained in effect for about 75 homes.