A head-on collision on Route 28 in Pittsfield on Monday closed the road for 3 1/2 hours and sent both drivers to hospitals, police said.

The collision happened about 3:30 p.m. when a male motorist heading north veered into the southbound lane and collided with a vehicle being driven by a woman, Sgt. Jeff Cain said.

A helicopter landed on Route 28 — which police closed to traffic — to pick up the wounded female driver and take her to Dartmouth-Hitchcock Medical Center in Lebanon. The male driver went by ambulance to Concord Hospital.

Cain said neither driver’s name was available last night as the investigation remained active. He said he had no information about the extent of their injuries.

No one else was traveling in either car.

Police have ruled out drugs and alcohol as factors in the collision.

“We’re still trying to determine if speed was a factor and we’re trying to determine what caused the northbound motorist” to cross into the southbound lane, Cain added.

Police rerouted traffic around the collision site until Route 28 reopened about 7 p.m.