The Apple Fire raged Wednesday morning in the mountains within the San Bernardino National Forest as firefighters worked to increase containment of the blaze, which has blackened 26,850 acres, destroyed 12 structures and was 20% contained.
The fire erupted in Cherry Valley about 5 p.m. Friday in the area of Apple Tree Lane and Oak Glen Road and investigators determined it was sparked by a malfunctioning diesel vehicle that was belching burning matter from its exhaust pipe, Cal Fire said.
Fire officials are estimating the blaze could be fully contained as soon as Aug. 17, according to Kate Kramer of the U.S. Forest Service.
The head of the Apple Fire is on a mountainside in San Bernardino County, according to the USFS. Two Cal Fire air tankers and 12 water-dropping helicopters were working to establish containment boundaries, as more than 2,500 personnel on the ground gradually attempted to encircle the brusher.
The fire is continuing to spread north, deeper into San Bernardino County, and east into the San Gorgonio wilderness, according to fire officials.
Firefighters hoped to take advantage of cooler temperatures and higher relative humidity Wednesday and increase containment lines, the USFS said.
One USFS firefighter suffered minor injuries overnight, Kramer said.
All mandatory evacuations associated with the Apple Fire were lifted Tuesday in Riverside County.
Evacuation orders were lifted in the unincorporated areas east of Oak Glen Road, west of Potrero Road, and north of Wilson Street, although non-mandatory warnings were still in effect east of Potrero Road, north of Morongo Road and west of Whitewater Canyon, the U.S. Forest Service reported.
In San Bernardino County, mandatory evacuation orders were unaffected east of Oak Glen Road. Non-mandatory evacuation warnings in San Bernardino County also remained in effect in Forest Falls, Rimrock and Pioneertown.
The American Red Cross closed its temporary evacuation center at Beaumont High School at 7 p.m. Tuesday, but residents under the Oak Glen evacuation order could receive assistance from the Red Cross by calling 571-595-7774.
Gov. Gavin Newsom announced the state will receive a Fire Management Assistance Grant from the Federal Emergency Management Agency to help ensure resources will be available to fight the brush fire.
The grant will also allow local, state and tribal agencies responding to the fire to apply for 75% reimbursement of their eligible costs, Newsom said.
Officials estimated that 2,600 residences and 7,800 people have been evacuated since the blaze began.
On Sunday morning, management of the incident transitioned to California Interagency Incident Management Team 2. A public information line was established at 909-383-5688.
The smoke column from the fire was visible throughout much of Southern California.
Along with county fire crews, personnel from the Calimesa, Morongo, Murrieta, Palm Springs, Cathedral City, Huntington Beach, Hemet, Pechanga, San Bernardino, Soboba, Los Angeles and Los Angeles County fire departments were sent to assist under a mutual aid request.
Anyone with further information about the start of the fires was urged to call the Cal Fire hotline at 800-633-2836. Callers may remain anonymous.