A fast-moving wildfire in the mountains of San Bernardino County grew Monday to nearly 6,300 acres, prompting the evacuation of thousands of residents, authorities said.
About 375 homes were under a mandatory evacuation order in the Summit Valley area and Hesperia, according to the U.S. Forest Service and the San Bernardino County Sheriff's Department.
About 5,000 homes were under a voluntary evacuation advisory in Hesperia and nearby communities, Sheriff's Department spokeswoman Cindy Bachman said.
After it was first reported about noon Sunday, the Pilot fire spread quickly in dry brush and timber. As of Monday night, the blaze was only 6% contained, said Justin Taylor of the U.S. Forest Service.
The cause of the fire is under investigation.
Firefighters have worked in the air and on the ground to build fire lines and snuff out the flames, said U.S. Forest Service spokesman Bob Poole.
"Because the vegetation is so incredibly dry, all it takes is a little spark and it's just been chewing through it," Poole said. "That's been our difficulty."
There has been no structural damage to homes in the rugged rural area, which has several horse ranches.
More than 840 firefighters have been assigned to battle the blaze, aided by five bulldozers and a fleet of helicopters and air tankers.
"Because of the aggressive attack by our firefighters, we were able to protect homes," Poole said. "These guys — they're highly trained, they're highly motivated and they're doing an incredible job in difficult conditions."
The mandatory evacuation order on Highway 173 extended from Highway 138 to Arrowhead Lake Road and from Hesperia Lake Place to Highway 173, fire officials said. In Hesperia, the evacuation order covers homes from Santa Fe Avenue to Lake Arrowhead Road as well as homes south of Ranchero Road, Bachman said.
The voluntary evacuation order included those north of Deep Creek Spillway, south of Rock Springs Road, east of the Mojave River and west of Kiowa Road, according to the U.S. Forest Service.
The American Red Cross has opened a shelter at Oak Hills High School. Pet owners can bring animals to the San Bernardino County Devore Animal Shelter.