At least one person died Tuesday evening in a crash caused by a landslide in unincorporated Napa County, according to the California Highway Patrol.
The incident was reported just after 5 p.m. near Highway 121, also known as Monticello Road, and Wild Horse Valley Road.
The crash reportedly involved rocks striking a vehicle, causing it to careen down an embankment and strike a tree, CHP officials said.
Witnesses reported seeing the car get hit by a rock or rock slide before the accident, the CHP said. There was too much loose rock and debris to get close to the crash, they said.
A Sig-alert was issued, closing Highway 121 in both directions between Vichy Avenue and Wooden Valley Road, according to the CHP. The roadway remained closed early Wednesday.
Officials are concerned about the stability of the road and nearby terrain. CHP reported that Caltrans on Wednesday plans to send a geologist to examine the hillside in question.
NBC Bay Area staff contributed to this report.