Updated

Thunderstorms across Southern California on Sunday brought flash floods that led to a few rescues, while thick debris flows cut off access to two mountain towns and stranded more than 2,000 people people.

About 1,500 residents of Oak Glen, and another 1,000 residents of Forest Falls in the San Bernardino Mountains were unable to get out because the roads were covered with mud, rock and debris, authorities said.

The stranded include 500 people who had arrived at a Forest Falls campground Sunday morning.

"Our concern is that they're isolated at that campground and no longer have access out of the mountain," San Bernardino County Fire spokesman Kyle Hauducoueur said.

Authorities made reverse 911 calls to urge residents to stay put while crews clear the roads with bulldozers.

Flash floods led to the rescue of at least two people in the San Bernardino Mountains. Hauducouer said a woman in Mt. Baldy was rescued from her house before it was immersed in mud. Four additional homes in the Bear Creek area were damaged by the debris flow, he said.

Monsoonal moisture brought brief but fierce storms to mountain, desert and inland areas.

The storms dumped as much as 3 ½ inches of rain on Forest Falls, the National Weather Service said.