Updated

A wildfire broke out Wednesday in a rural area in Southern California and grew with extreme speed, threatening three communities where people were evacuated and apparently burning at least two homes.

The fire broke out about 2 p.m. and about four hours later, it had surged to 5,000 acres, or nearly 8 square miles, according to the California Department of Forestry and Fire Protection.

TV news cameras have showed at least five structures burning in isolated areas, and at least two of them appeared to be homes, but fire officials would not confirm that homes had burned.

More than 400 firefighters, five helicopters and five air tanker planes were working to get ahead of the flames in Riverside County near Banning.

One firefighter has been injured, but details are unknown.

Mandatory evacuations have been called for the rural communities of Poppet Flats, Twin Pines and Silent Valley. It wasn't immediately clear how many homes or people were affected.

Evacuation centers were set up at high schools in Hemet and Banning.

Temperatures in the area were in the high 80s and low 90s on Wednesday afternoon, with winds blowing up to 20 mph.

State Route 243, a mountain road between Banning and Idyllwild, was closed to non-emergency traffic.

About 30 miles to the southwest, firefighters were working on a 1,100-acre wildfire that has been burning since Monday southwest of Lake Elsinore. That blaze is 73 percent contained and full containment was expected by Friday.

The blaze caused evacuations the night it broke out, but the last of them were called off Tuesday night.