Firefighters had the 160-acre blaze about 20 percent contained by 5 p.m. Thursday.
The blaze was reported at about 1 p.m. near Interstate 15, charring approximately 150 acres between Corona and Lake Elsinore as of Thursday afternoon.
More than 80 firefighters were battling the blaze.
The area consists of homes, orange groves and open vegetation. No evacuations were ordered and no injuries were reported.
The fire was burning in the hills above the Trilogy Golf Club, and was not affected.
The cause of the blaze was not immediately determined.