LOS ANGELES (CNN) -- Firefighters, air tankers and helicopters replaced hikers and campers in the recreation-rich San Gabriel Canyon on Monday, September 3rd after a wildfire forced authorities to close the area for Labor Day.
Authorities evacuated the canyon Sunday after the fire broke out in Angeles National Forest, an urban recreation area near Los Angeles that's popular with hikers, campers and off-road vehicle enthusiasts.
About 50 residents and 1,000 campers were evacuated, CNN affiliate KABC reported.
"I know we have some neighbors up there that didn't leave. We're really worried about them," evacuee Toni Kova told KABC.
Kova and her husband live in Camp Williams, which was evacuated Sunday.
"We saw the smoke and the fire coming over the hill. The river is literally our front yard and the mountains that the fires were coming over," she said. "We were like, we gotta start packing up."
Between 10,000 and 12,000 people use the area during an average holiday weekend, according to Inciweb, the government fire-tracking website.
Structures in Camp Williams, a camping and recreational vehicle resort, are in danger from the fire even though it is burning to the northeast toward a wilderness area, Inciweb said.
About 400 firefighters, six heavy air tankers and eight helicopters are working on the blaze, which had burned through about 4,000 acres of brush by Monday morning, according to Inciweb.
Inciweb said the cause of the fire was under investigation. CNN affiliate KTLA-TV in Los Angeles, citing a U.S. Forest Service official, reported the fire began when a car caught fire.
The r has opened an evacuation center in Glendora, California.