An out-of-control wildfire that broke out in a forested basin near a Southern California dam triggered the evacuation of about 300 homes late Saturday, authorities said.

The fire, which was reported shortly after 6 p.m. in the Prado Dam Flood Control Basin and spread to 300 acres by early Sunday.

Capt. Mike Mohler of the California Department of Forestry and Fire Protection said firefighters on the ground were hampered Saturday by difficult access to the raging blaze.

"The fire is fueled by thick brush in a riverbed that hasn't burnt in years," he said. "The fire is creating its own weather, so firefighters are having difficulty getting in there."

He said the flames were about a half-mile north of a residential area along the border of the cities of Norco and Corona. A mandatory evacuation was ordered for about 300 homes in the area.

"The fire is heading toward a populated area," Mohler said.

The fire, visible from State Routes 71 and 91, sent a large plume of smoke that could be seen miles away. The cause of the blaze was under investigation.