A fire scorched 200 acres of tinder-dry brush in the Angeles National Forest before firefighters contained it late Saturday, forestry officials said.
Fire officials still had not determined the cause of the fire, which broke out in rugged terrain in the San Gabriel River watershed, U.S. Forest Service spokesman Bob Swinford said.
Firefighters expected to have the blaze under control by midnight, Swinford said.
In addition to three water-dropping helicopters, three air tankers splashed a red fire-retardant chemical on the nearly inaccessible mountain slopes near the 5,826-foot level of Rattlesnake Peak, Swinford said.
No structures were threatened and no evacuations were ordered, despite a heavy volume of visitors for the three-day Labor Day weekend, Swinford said.
Firefighters from the U.S. Forest Service, Los Angeles County Fire Department and Glendora Fire Department battled the flames. Additional crews were requested from outlying areas, Swinford said.
Temperatures rose into the 90s Saturday afternoon, but winds were calm and the humidity levels high, Swinford said.
The fire erupted at 12:04 p.m. a short distance from California 39, seven miles north of Glendora, near a tree plantation reforestation area, the spokesman said.