A crash that shut down rural Highway 20 near Ukiah for hours Friday started with a pickup driver who crossed double yellow lines and smashed into an oncoming big rig, according to the CHP.

The 7:15 a.m. collision occurred at a bridge over the Russian River, in Redwood Valley, north of Ukiah.

The damaged rig leaked about 190 gallons of fuel, and a fire broke out, with flames spreading to the bridge.

The highway remained closed early Friday afternoon, while cleanup continued and a review was conducted of the bridge's structural integrity, said CHP Sgt. Lanika Lee-Escorpiso.

After the two vehicles collided, the semi-truck and trailer began to jackknife and sideswiped another vehicle.

Injuries were minor and no one was transported to a hospital.

What caused the driver to move into the opposite lane remained under investigation Friday.

Traffic was diverted to nearby roads.