AUBURN — Authorities are investigating a crash early Sunday morning that sent two people to the hospital and left one in a medically induced coma.

Alan Leonard, 37, of Hebron remained in a medically induced coma Sunday night, according to Trooper Bernard Campbell of the Maine State Police. He was listed in stable condition at Central Maine Medical Center, where he was taken with head injuries following the 12:51 a.m. crash on the southbound off-ramp at Exit 75 of the turnpike.

The owner of the minivan involved in the single-vehicle crash, Jay Nelson, 32, of Hebron was treated and released at Central Maine Medical Center with a broken wrist, Campbell said.

"We're not sure who was driving. No one claims they were driving at this point," Campbell said Sunday night.

Campbell said that the minivan was traveling on the southbound exit ramp in Auburn when the driver lost control, went off the left side of the road up an embankment and hit a tree. By the time police and emergency crews arrived on scene, everyone was out of the vehicle — including Leonard, who is thought to have been in the front passenger seat.

Four other people were riding in the vehicle: Nicole Wilkie, 29, of Oakland, Christina Benson, 26, of Mechanic Falls, Kevin Leighton, 32, of Minot and Howard Washburn, 34, of Oxford. Investigators believe they were traveling from a Lewiston bar back to the Hebron area.

Campbell said that investigators believe that both alcohol and speed played factors in the crash. But because no one would admit to driving the vehicle, he said that it made the investigation difficult. Adding to those difficulties was the fact that all occupants in the vehicle — including Leonard, who suffered the most severe injuries — were out of the wreckage and refusing to talk to police.

Campbell said that under state law authorities were not able to force a blood test on any of the occupants in the car because none of them would admit to driving. None of the occupants appeared to be wearing their seatbelts.