With the massive wildfire burning north of Los Angeles more than half contained, hand crews were working Sunday to keep the fire's eastern flank from crossing a rural mountain highway, a U.S. Forest Service spokeswoman said.
The fire, which started Aug. 26, has killed two firefighters, blackened nearly 246 square miles (637 square kilometers) of the Angeles National Forest and destroyed at least 76 homes. Fire agencies so far have spent $43.5 million fighting the blaze.
Authorities on Sunday were trying to determine who set the deadly fire.
At least a dozen investigators were working to analyze clues found at a burnt hillside near Angeles Crest Highway where the fire started. But officials, who say the cause of the fire was arson, were hesitant to release any of their findings to the media.
The fire was 51 percent contained Sunday as crews built new protective lines near Highway 39 in the San Gabriel Wilderness, U.S. Forest Service spokeswoman Jennifer Sanchez said.
No homes were immediately threatened.
The weekend weather forecast called for cooler temperatures and slightly higher humidity that could help firefighters further surround the blaze. Because of the reduced heat, about 400 firefighters assigned to protect structures were dismissed Saturday. About 4,800 firefighters remained.
Los Angeles County firefighters Tedmund Hall and Arnaldo Quinones were killed Aug. 30 while seeking an escape route for their inmate fire crew after flames overran their camp on Mount Gleason. The two died when their truck plunged 800 feet (244 meters) off a steep mountain road.
Sheriff's detectives opened a homicide investigation after the fire was ruled arson earlier this week, and Gov. Arnold Schwarzenegger has offered $100,000 for information leading to the arrest and conviction of the culprit.