Firefighters Sunday were battling a brush fire that was burning approximately 40 acres in Thermal and prompted the closure of Highway 86.
The fire was reported around 2:40 p.m. Sunday near the intersection of Avenue 72 and Buchanan Street, according to the Riverside County Fire Department.
Responding firefighters reported the fire burning in heavy fuels at a dangerous rate of spread and additional engines were requested.
As of 4 p.m. Sunday, the fire was holding at 40 acres but had slowed its rate of spread.
The California Highway Patrol issued a sigalert for the closure of both directions of Highway 86 near 66th Avenue.
No injuries were immediately reported.
The cause of the fire was unknown.