Firefighters were battling an 800-acre brush fire Thursday evening that was burning across dry hillsides in western Riverside County near Corona.
No structures were immediately threatened, but officials were warning nearby residents to be ready in case they were ordered to evacuate, the Riverside County Fire Department said.
The fire was started by mowing equipment, authorities said.
More than 250 firefighters, along with three water-dropping helicopters and four air tankers, were attacking the blaze, which broke out shortly before 1 p.m. near the community of Home Gardens, east of Corona. They were aided by 10 ground crews and several bulldozers that were cutting breaks along the fire flanks.
"It's looking like we're getting a pretty good handle on it," Capt. Phil Rawlings said in a telephone interview from the scene.
The fire was 50% contained by late Thursday. Authorities said full containment was expected by 6 a.m. Friday.
Temperatures were in the low 80s and winds gusts were 15 mph, fire officials said.