The blaze began Thursday afternoon in an orange grove in Temescal Canyon, a hilly area south of Corona.
U.S. Forest Service spokesman Jake Rodriguez says the fire is 60 percent contained Friday and crews expect to surround it by Sunday.
No homes are threatened. Two firefighters have been treated for minor injuries.
About 275 firefighters, aided by aircraft, are on the scene some 50 miles east of Los Angeles.
The cause of the blaze hasn’t been determined.
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