Interstate 15 in Hesperia remains closed in both directions as crews try to extinguish a fire that burned all night at a bridge construction site.
Commuters on Tuesday are urged to find alternate routes, including interstates 138 and 18. Caltrans says I-15 could remain shut down for up to two days.
Officials say drivers should stay away from the Cajon Pass, which is just south of the area closed by the fire.
The freeway - Southern California's main connector to Las Vegas - was closed around 1:30 p.m. Monday because of falling debris.
San Bernardino County Fire Capt. Josh Wilkins says the blaze was started when a construction worker's blowtorch accidentally ignited the wooden supports of the Ranchero Road overpass bridge.