The driver of a car that collided with a school bus Wednesday morning in New Gloucester is still in critical condition and police said it could take some time to determine what caused him to cross the centerline.

Robert Doughty Jr., 59, of Yarmouth was taken by LifeFlight helicopter to Central Maine Medical Center in Lewiston shortly after the crash and was being treated for life-threatening injuries.

He remained in critical condition Thursday, according to hospital officials.

Lt. Tom Williams of the Cumberland County Sheriff’s Office said investigators have not had a chance to interview Doughty.

“Right now, everything is on the table, from some kind of impairment or whether he had a medical condition,” Williams said Thursday.

Doughty was driving a 2015 Acura sedan northbound on Route 231 when he crested a hill near the intersection with Penney Road and went off the right side of the road. He then over-corrected and collided head-on with a bus traveling in the opposite direction.

The bus, driven by Kathleen Allen, 56, of Gray, was carrying 10 elementary school students but none was injured.

The children were loaded onto another bus and taken to school. Allen was treated for minor injuries.

Doughty’s car was destroyed and the bus sustained extensive front-end damage.

Williams said police are still investigating the cause and have taken blood samples to determine whether Doughty was impaired. They also will review video footage from the bus’s camera and attempt to communicate with Doughty as soon as possible.