Angeles National Forest officials said the Fork Fire was located off of Highway 39 and East Fork Road.
Hundreds of recreational visitors were evacuated as crews battled the nearby flames.
High temperatures and dry brush helped feed the fire, according to fire officials.
An injured firefighter had to be airlifted to safety after he was hurt by falling rocks while battling the blaze, according to L.A. County sheriff's officials.
VIDEO: #LASD Air Rescue 5 hovers over #ForkFire while rescuing an injured firefighter, victim of rockfall. LASD SEB Tactical Medics hoist firefighter into the aircraft and transport him to trauma center. Public safety #teamwork. pic.twitter.com/JU2pQ9tiZ0— SEB (@SEBLASD) September 10, 2018
Highway 39 was closed 2 miles above Sierra Madre Boulevard during the firefight.
As Sunday night, forest officials said the blaze was 0 percent contained.