LOS ANGELES — Emergency crews shoveled mud from a section of Interstate 5 north of Los Angeles after flash flood debris blocked the important highway, stranded hundreds of vehicles, and forced some motorists to take refuge on top of their cars.

Excavator trucks scooped and hauled away mud in the darkness Thursday night and the cleanup continued well into Friday, leaving thousands of drivers searching for alternative routes.

About 15 cars remained wedged in the debris and needed to be towed out.

There were no reports of deaths or injuries from the flooding Thursday at Fort Tejon, about 75 miles north of downtown Los Angeles, brought on by a weather system that produced powerful afternoon thunderstorms in the mountains and deserts.

A second highway was closed Thursday night following a separate mudslide. And a number of secondary roads were left impassable from mud and some residents were trapped in their homes.

Officials expect the freeway to be reopened around 2 p.m. Friday, California Highway Patrol Officer Tony Polizzi said.

The affected section of I-5, one of the state’s major north-south arteries, carries traffic among steep mountains over a pass rising to an elevation of more than 4,100 feet between the Central Valley and metropolitan Los Angeles.

After removing the debris, a geologist will check the stability of nearby slopes before the freeway is reopened, California Department of Transportation spokeswoman Lauren Wonder said earlier.

“There could always be more slide that comes down onto the road,” she said. “Our engineers are always very careful so they make sure in a flood situation, any hillside is secure.”

The National Weather Service said a flash flood watch would be in effect again Friday afternoon and early evening for the mountains and deserts because of the threat of more severe and slow-moving thunderstorms, which raises the potential for flash floods and debris flows.

Photos of Interstate 5 posted on social media showed the freeway in disarray, with semi-trucks and cars sitting askew, stuck in mud that in some cases surpassed their wheels.