A big rig overturned on Lucas Valley Road east of Big Rock on Thursday morning, forcing authorities to close the road in both directions as crews scrambled to clean up spilled cargo.

No one was hurt in the accident, reported just before 6:30 a.m. The road, between Westgate Drive and Big Rock, was expected to be closed until 10 p.m. Thursday, California Highway Patrol officials said. The CHP urged drivers to make alternate plans Friday as one-way traffic control continued from 7 a.m. to 1:30 p.m. as crews completed cleanup efforts.

The truck, carrying eight 250-gallon containers of paint, was headed to Nicasio Yard, Marin County’s road maintenance facility.

The driver, 28-year-old Hugo Zavala-Barrera, of Mendota, in Fresno County, was traveling through a switchback turn when the wheels of his trailer dropped off the right side of the roadway, said CHP Officer Andrew Barclay. The containers came loose and toppled into the ravine, spilling gallons of paint and triggering a full hazardous materials team response, Barclay said. No citations have been issued, he said.

Representatives from the Environmental Protection Agency, California Department of Fish and Wildlife, Marin County Sheriff’s Office, Marin County Fire Department, Skywalker Fire Department, Bayview Environmental Services and Marin County Roads responded to the scene and began the recovery and cleanup of the hazardous materials.

Oversized tow equipment was required to right the truck.

“That is a watershed area,” said Marin County sheriff’s Lt. Doug Pittman. “The concern was, the contamination from the paint was getting into the watershed property.”

Because the creek is mostly dry, due to the drought, the contamination is not as bad as it could have been, Pittman said.

“If it was raining, that water that flows off the hillside runs down to the creek and could eventually flow to the bay,” he said.

There is an advisory sign that recommends drivers with trucks longer than 40 feet avoid the road. The length of the truck, registered to Fresno-based JL Freight Line LLC, was not immediately available. A representative of JL Freight Line LLC could not be reached for comment.

“The majority of the time, the primary collision factor is running off the roadway, meaning they take the turn too tight,” Barclay said. “The truck clears, but the trailer wheels do not. That is something we have discussed with the county to maybe change it to a regulatory sign.”

Craig Parmley, superintendent of road maintenance at the Nicasio facility, said they advise drivers to avoid the winding road.

But “they do a GPS or Google Maps search and it sends them over Lucas Valley,” he said.