The fire, dubbed the Merwin Fire, was reported near Merwin Street and Campbell Avenue at about 8:40 p.m.
As of 11:15 p.m., it had scorched approximately 175 acres with a containment of 5 percent. The blaze was not threatening any structures. A total of 125 firefighters are battling the fire which is burning toward Lake Perris State Park.
A group camp area in Lake Perris State Park has been evacuated. The cause of the fire has not been determined. No injuries have been reported.