The fire began about 3 ½ miles east of California 39, midway between Camp Williams Resort and Burro Canyon Shooting Park, Wagner said. The cause of the fire remained under investigation.
A burned car was found in the area, but it was unclear if it was the source of the fire or was simply consumed by the flames, authorities said.
The area where the fire was burning, along the East Fork of the San Gabriel River, is a popular spot on holiday weekends for campers and hikers, particularly in summer.
The area is patrolled by the Los Angeles County Sheriff's Department, California Highway Patrol and U.S. Forest Service, which has jurisdiction over the 640,000-acre Angeles National Forest. Hundreds of people live in trailers and cabins in the vicinity of Camp Williams Resort, which is located on the East Fork and includes a campground, mobile home park and restaurant.
Standing outside the Camp Williams Cafe, Jill Coverdale watched the small red-orange flames burning at the top of Shoemaker Canyon Road.
She was one of the few residents who stayed behind, ignoring mandatory evacuation orders as the wildfire burned along the ridge of the canyon, just yards from the Camp Williams Mobile Home Park.
"It was unreal," Coverdale recalled. "The flames were huge, and the campground was packed with people."
Three Idaho wildfires resist containment efforts • Firefighters in Idaho continue to battle three large wildfires that are proving difficult to bring under control.
In central Idaho, the 194-square-mile Halstead Fire is only 7 percent contained and on Sunday was about 100 yards from power lines that provide power to the mountain tourist town of Stanley.
The Custer County Sheriff's Office late Saturday told residents of about 30 homes between Sunbeam and Yankee Fork to evacuate, and that the agency couldn't guarantee the safety of those who remained behind.
The fire late on Saturday also sent out embers across a fire line that started spot fires on the east side of Yankee Fork Road.
"But firefighters were able to swoop in and extinguish all the spot fires," said fire spokesman Eric Mosley.
He said crews on Sunday have been setting back burns using firefighters on the ground and starting fires using helicopters to drop small incendiary spheres. He also said firefighters painted the wooden power poles with a fire-resistant coating and firefighters are positioned to protect them from fire.
The fire has moved to within about three miles north of Stanley, but State Highways 75 and 21 remain open.
Mosley also said there are modern mining operations in the area that fire crews are protecting as well as historic mining structures, including a large dredge. About 560 personnel are assigned to the fire that is also being fought by seven helicopters.
To the south, back burns on the 226-square-mile Trinity Ridge Fire have been effective in protecting Featherville and an evacuation order was lifted Sunday morning. Crews in recent days have been trying to slow the fire's growth toward the Middle Fork Boise River with helicopter water drops. About 1,200 personnel are assigned to the fire that is 31 percent contained.
Along the Idaho-Montana border, fire managers say the 329-square-mile Mustang Complex of fires will be difficult to contain without rain or snow.
Fire officials on Wednesday issued various evacuation levels for residents near the fire that remain in effect. Residents along Highway 93 between Hull and Sheep have been advised to leave immediately.
More than 900 wildland firefighters are fighting the blaze that is 16 percent contained and has burned across the Idaho border into Montana. Officials say more firefighters are being called in.
Firefighters make headway against Nebraska blazes • Some firefighters who have battled the western Nebraska and South Dakota wildfires for nearly a week are being sent home, a fire official said Monday.
The three fires have burned nearly 260 square miles, but firefighters have made considerable progress on the Douthit and West Ash fires near Chadron, Neb., said information spokesman Neal Kephart.
"We're getting a good handle on those fires and releasing personnel and equipment," Kephart said. The Douthit fire was 99 percent contained and the West Ash fire is 55 percent contained.
He estimated as many as 700 people, including firefighters, managers and support personnel, were working those fires. He expects the number could drop to 400 by Monday night.
Kephart said at least five homes and a number of other structures have been destroyed by the two fires, but that officials will have a better idea of the damage once assessment teams surveyed the area.
Crews were also making good progress against the Wellnitz fire, which is burning north of Rushville and into South Dakota. Officials said if containment efforts continue, some local firefighters could be released soon.