The Fairmont Fire erupted about 10:30 a.m. near 160th Street and Lancaster Road, about 15 miles west of Lancaster, according to the Los Angeles County Fire Department.
Fixed-wing aircraft were assigned to the second-alarm blaze, which was first reported as a 25-acre brush fire that was threatening structures.
LA County fire officials tweeted minutes later that the blaze was estimated at 125 acres in size and the structure threat was diminished.
No evacuation orders were in place during the firefight.
By 11:30 a.m., fire officials said the forward progress of the Fairmont Fire was stopped as it stood at 170 acres. Fixed-wing aircraft were also released.
City News Service contributed to this report.