PHOTOS: Flash-flooding, mudslides in San Bernardino Mountains

FOREST FALLS, Calif. (KABC) -- A river of mud swept through the San Bernardino Mountains on Sunday, killing one person and leaving thousands stranded.

One adult died after being trapped in a vehicle that was swept off Bear Drive in the Mount Baldy area in flash-flood conditions.

In the Oak Glen area, approximately 1,500 residents were unable to get out, according to Cal Fire. As many as 3,000 people were estimated to be stranded in the Forest Falls area.

As many as 60 people were stranded Sunday evening at the Big Falls Campground near Valley of the Falls Drive, according to the San Bernardino County Fire Department. No injuries were reported there. The department said there were three major slides in the area with debris about 12-15 feet high, 75 feet wide and a quarter-mile long.

See photos of the damage above.