FAIRFIELD, Calif. -- A chemical spill near Fairfield Monday morning forced California Highway Patrol to shut down more than nine miles of state Highway 12 through Napa and Sonoma counties for more than six hours.

The crash happened around 5:15 a.m. on Highway 12, about a mile and a half east of the Napa County line, CHP Officer Willy Williford said.

Williford said the driver of an eastbound Ford Ranger pickup lost control for unknown reasons and crashed. The truck came to rest on its left side in the westbound lane of the two-lane road, he said.

Chemicals spilled in the crash, and the CHP shut down the entire roadway and called in the county hazardous materials team, Williford said.

The company that owns the truck, Orkin, also sent in a cleanup crew, he said.

The roadway was reopened at about 12:15 p.m.

Williford said traffic was slightly backed up on nearby Interstate Highway 80 and state Highway 29, but he said the congestion was not severe.

"I think we can pretty much attribute that to the fact that people have taken the week off for Christmas," he said.

The driver complained of shoulder pain but no other injuries related to the crash were reported, Williford said.

Williford said the roadway was wet but it remains unclear what caused the driver to lose control.