CORONA -- A brush fire burning near Corona in western Riverside County is now 50 percent contained, with full containment expected by midnight, according to authorities.

The fire broke out about 2 p.m. Wednesday south of State Route 91, and quickly burned about 30 acres of light fuels.

Riverside County crews have been joined by firefighters from Orange County, the Cleveland National Forest and city of Corona. About 200 firefighters were called to the blaze in all.

Two aerial tankers and three water-dropping helicopters were helping ground crews.

No injuries have been reported and no structures are threatened.

Temperatures are in the upper 70s with 17 mph winds and 40 percent relative humidity.