The fire burned four cabins and caused five minor injuries to firefighters.
Authorities told CBS2’s Tom Wait on Thursday that they were narrowing on arson as the cause.
Authorities said about 1,900 firefighters were working around the clock to battle the blaze.
The blaze located near 160th Street West and Lancaster Road was initially reported around 1:50 p.m. Friday, according to the Los Angeles County Fire Department.
The fire was reported at 2:30 p.m. at Mission Inn Avenue and Scout Lane, near a Boy Scout camp adjacent to the Santa Ana River bed.
The Pine Fire was first reported at 1:20 p.m. Friday.
The time of total containment has yet to be determined, said a department dispatcher.
The Silver Fire, which burned 20,292 acres near Banning, was fully contained Monday.
A brush fire that charred about 125 acres and forced the evacuation of 200 homes in Monrovia is 85 percent contained.
A wildfire in the heavily vegetated Santa Ana River bottom has been held to 311 acres, despite gusty Santa Ana winds, extremely dry conditions and temperatures in the 80s.
The “Lookout” fire near the Painted Cave area of Santa Barbara is 75 percent contained as of Thursday morning.
A a wildfire burning in rugged areas of the San Gabriel Mountains northeast of Los Angeles is expected to be fully contained by Thursday.
A 50-acre brush fire burning south of Hemet has been fully contained, according to authorities.
brush fire that burned 145 acres in the Angeles National Forest near Gorman was knocked down Sunday evening.
Crews are still fighting a stubborn wildfire in rural Riverside County that has burned through 355 acres of heavy vegetation and destroyed one home.