The Snow Fire burning northwest of Palm Springs was 80% contained Friday morning, with much of the fire activity confined to pockets of remote wilderness away from residential areas.
The fire has blackened 6,254 acres since igniting on Sept. 17 in the 15000 block of Snow Creek Road, according to the Riverside County Fire Department.
Firefighters were expected to have containment lines dug around the fire's entire perimeter by Oct. 1.
The cause of the blaze has not been officially determined, although the California Highway Patrol reported that a work truck caught fire about 2:40 p.m. near Snow Creek Village, and the fire spread to nearby vegetation.
"We do know that there was a car there, but other than that, we don't know how it happened," U.S. Forest Service spokeswoman DeLyn Sieliet said.
Sieliet said Cal Fire and the Riverside County Sheriff's Department were handling the investigation.
One firefighter suffered injuries during the firefight on Saturday, according to Sieliet. The severity of the injuries was not disclosed.
No structural damage has been reported.
The flames have spread into the San Bernardino National Forest and the Santa Rosa and San Jacinto Mountains National Monument, prompting a multi- agency response.
Over the weekend, the flames were threatening about 450 homes in communities near Snow Creek and Windy Point, but firefighters mitigated the threat to those areas and canceled all evacuation orders Sunday. A temporary evacuation point in Cabazon operated by the American Red Cross was also shuttered at that time.
A total of 35 firefighters remain assigned to the firefight from several agencies, including the U.S. Forest Service and Bureau of Land Management. They were being assisted by a water-dropping helicopter.