Three victims injured in Friday’s multi-vehicle crash that shut down Highway 121 for hours Friday remain hospitalized, according to the California Highway Patrol.

At around 2:30 p.m. Friday, a rig hauling boulders was traveling southbound toward the Sonoma County line, when it flipped over and slid onto the road as it approached a 40 mile-per-hour curve one mile from the Napa-Sonoma County line, according to the CHP.

Three vehicles traveling toward Napa could not avoid the large rocks that spilled onto the highway from the 1997 Peterbuilt truck and trailer, according to the CHP. A 2001 Mitsubishi Montero Sport also could not avoid the truck.

Robert and Kathleen McDonald of Napa suffered critical injuries when a large boulder from the rig hit their 1997 Porsche, causing it to spin into the right shoulder, according to the CHP.

The McDonalds, both 45, were listed in guarded condition Saturday at Queen of the Valley Medical Center, according to the CHP and the hospital.

Passers-by pulled Kathleen McDonald out of the car while firefighters used the “Jaws of Life” to extricate her husband from the driver’s seat, CHP Officer Tom Lipsey said.

Passers-by also helped Rakhwinder Singh, 24, of Santa Rosa, from the 1998 Toyota Camry he was driving before it caught fire, Lipsey said. The Toyota Camry spun and hit a concrete wall near a 20-foot drainage ditch, according to the CHP.

“He was lucky,” Lipsey said.

Singh was listed in stable condition Saturday at Queen of the Valley Medical Center, according to the hospital.

Alfred Lyles, 64, of Sacramento, the driver of the Mitsubishi, was treated at the scene for minor injuries and released, according to the  CHP.

Kevin Stewart, the driver of the rig owned by Darrah Trucking and Excavation of Martinez, was hauling his second load from a construction site, Lipsey said Saturday.

Stewart, 48, was not injured, Lipsey said.

The CHP is still piecing together the cause of the accident, Lipsey said.

Alcohol was not a factor in the crash and there was no reckless driving, he said.

The road remained closed while crews cleaned up the debris and Caltrans repaired deep gouges into the road and the guardrail along the shoulder.

Highway 121 reopened at around 9 p.m., Lipsey said.