California ? 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 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.