A pack of loose cows caused a non-injury accident along Highway 16 near Sunrise Boulevard in rural Sacramento County.
More than 30 cows escaped through a hole in a fence along the highway, also known as the Jackson Highway, and ended up in the road, said Sacramento County sheriff's spokesman Tony Turnbull.
A pickup truck driver headed westbound along the highway did not see the cattle until it was too late, hitting 11 cows, Turnbull said.
Of the 11 hit, nine cows died as a result of their injuries, Turnbull said, noting two more may need to be put down as well.
The truck was heavily damaged in the crash, but the driver was not injured.
That particular stretch of road was closed for about an hour after the crash. It has since reopened.