A burning RV started a stubborn brush fire Sunday.

The fire was reported at about 10:45 a.m. Sunday on In-ko-Pah Road at the top of Mt. Springs Grade. The RV, with a 30-foot trailer, apparently caught fire and that ignited brush on the roadside. The RV and trailer were totally involved by the time firefighters arrived. The spreading brush fire burned several utility poles and continued to burn in the rugged terrain. The blaze developed into a three-alarm fire that had crews from throughout the Imperial Valley, eastern San Diego County as well as state and federal agencies involved. Traffic along Interstate 8 was stopped in both directions at times as heavy smoke and the spreading flames crossed the freeway. Fire crews remained on the scene until about 6:00 p.m. knocking down hot spots.