A Santa Rosa woman was arrested Thursday night on suspicion of driving under the influence of drugs after she veered off Highway 101 in Petaluma and into a seasonal pond on the north end of town.

Lauren Forest-Knowles’ white Honda sedan became stranded for several hours in knee-deep water in a low-lying area east of the highway just south of the Penngrove exit, the CHP said.

A motorist traveling behind her saw her car suddenly leave the road about 6 p.m. and crash through a chain link fence before plowing into the water, Petaluma Fire Battalion Chief Mike Medeiros said. The witness got out of his car and waded out to Forest-Knowles, 32, to see if she was alright before emergency responders could get to the scene, Medeiros said. Firefighters ended up helping her from the vehicle and leading her out to the road.

She was disoriented, and emergency personnel thought she might have suffered a medical problem that caused her to lose control of the car, Medeiros said.

She was taken to Petaluma Valley Hospital as a precaution but was later arrested on suspicion of DUI, the CHP said.