Firefighters were working to contain a large brush fire that broke out south of Hemet, in unincorporated Riverside County, on Thursday.

The flames were first reported just before 2:20 p.m. in the 34000 block of Rawson Road, according to Cal Fire Riverside.

Just two hours later, it had grown to 300 acres and destroyed an unoccupied structure, and by 7:20 p.m. it covered 1,261 acres, officials said.

It was 40 percent contained, and by 10 p.m. it was no longer making forward progress, firefighters said.

The threat had prompted officials to place about six homes under a mandatory evacuation order, but the residents were allowed to return home after 10 p.m.

The blaze was being dubbed the Patterson Fire.

Aerial video showed patches of smoke and flames covering the foothills region that lies south of Diamond Valley Lake. Fire helicopters could be seen extracting water from the lake to dump on the fire.

Airplanes were also dropping lines of fire retardant in attempt to keep the flames from spreading.

Smoke was billowing north, toward the communities of Winchester and Hemet.

Nearly 100 firefighters were at the scene working to extinguish the flames.