A fire that's destroyed a half-dozen vacant structures and blackened an estimated 300 acres in the Angeles National Forest northeast of Castaic was about 30 percent contained, authorities said.
No injuries were reported as a result of the so-called Warm Fire, which broke out about 3:30 p.m. Sunday in the area of Lake Hughes and Warms Springs roads, said Joel Gonzalez of the U.S. Forest Service.
The cause of the fire was under investigation.
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Late Sunday night, the fire was listed as uncontained and burning "aggressively" in a southerly direction, according to the U.S. Forest Service.
After daybreak Monday, the fire was about 10 percent contained, and the size -- originally listed at 500 acres -- was determined to be about 300 acres after more precise mapping was completed.
Late Monday morning, the fire was listed at 30 percent contained.
The Forest Service reported that six vacant structures had burned. At least some of the destroyed buildings appeared to be at the shuttered Warm Springs Rehabilitation Center in the 38200 block of Lake Hughes Road, according to Los Angeles County sheriff's Sgt. Brian Allen.
Firefighters were fighting the blaze from the ground and air. About 150 personnel were assigned to the battle, Gonzalez said, noting that some personnel and aircraft were diverted from another fire in the region.
Air drops were not feasible at night due to power lines in the area.
No evacuations were immediately ordered. Area temperatures topped 105 degrees on Sunday, according to the National Weather Service.
Lake Hughes Road was closed between Castaic and Elizabeth Lake, according to the USFS.