A California wildfire raging through dry brush and timber east of Los Angeles, forcing thousands of people from their homes, was likely sparked by burning soot from the exhaust of a diesel truck, investigators said on Monday.

A firefighter tries to extinguish a wildfire in the village of San Cristobal near Monterrey, Spain on Wednesday. The fire began at 2:45 pm (local time) in the parish of San Millao, affecting 60 hectares, according to provisional data. Photo: AFP

The blaze, dubbed the Apple Fire, has scorched more than 10,500 hectares since erupting Friday in the Riverside County community of Cherry Valley, about 120 kilometers east of Los Angeles, and was only 5 percent contained as of Monday, fire officials said.

The fire posed an immediate threat to some 2,400 homes, prompting mandatory weekend evacuations of some 7,800 residents, said Fernando Herrera, a Riverside County Fire Department captain and spokesman for the California Department of Forestry and Fire Protection (CalFire). One house and two outbuildings were destroyed, CalFire said.

By Monday the flames had spread primarily to the east and north into rugged wilderness of the San Bernardino National Forest, and away from densely populated areas, US Forest Service spokesman David Cruz told Reuters. But all evacuation orders remained in effect, he said. The fire resulted from a "vehicle malfunction, specifically, a diesel-fueled vehicle emitting burning carbon from the exhaust system," based on physical evidence and multiple eyewitnesses.

Herrera said particles of soot from the unidentified vehicle ignited dry grass along a roadside that grew into the larger fire.
Newspaper headline: Diesel truck soot likely sparked major wildfire