A Sonoma man was arrested for suspicion of driving under the influence of prescription drugs and marijuana after a head-on collision Thursday in which two women were injured, the CHP said.

William Woodall, 31, told officers responding to the 2:30 p.m. crash that he'd drifted over the double yellow line on rural Bennett Valley Road and struck an oncoming Ford F-150, the CHP said.

Officers observed his apparent impairment and, upon questioning, learned he at least had taken a prescription drug, authorities said.

Woodall had been westbound near Old Bennett Ridge Road when he hit the eastbound Ford pickup driven by Deborah Poore, of Sonoma. The truck continued off the road and into a tree, injuring Poore, 52, and her passenger, Mary Bajza, 67, also of Sonoma, the CHP said.

The two women suffered moderate injuries in the crash and were taken to Santa Rosa Memorial Hospital for treatment, authorities said.

Woodall was arrested for suspicion of felony driving under the influence and was booked into the Sonoma County Jail. He was released after posting bail, jail personnel said.

The crash closed Bennett Valley Road for approximately two hours Thursday, Officer Jon Sloat said.