MECHANIC FALLS, Maine >>A mechanical problem caused a Jeep towing a wagon full of passengers to lurch down a steep hill and slam into a tree during a Halloween-themed hayride in the woods, killing a teenager and injuring more than 20 other people, authorities said.

Investigators were inspecting the Jeep to try to determine exactly what kept it from stopping on the hill, and state police were calculating the passengers’ weight to determine if the hay wagon was overloaded and whether that contributed to the mechanical problem, Sgt. Joel Davis of the state fire marshal’s office told reporters.

The Saturday night crash during the Gauntlet Haunted Night Ride "threw everyone off the trailer and into each other and into trees," Davis said.

Seventeen-year-old Cassidy Charette, of Oakland, died from head injuries, state police spokesman Steve McCausland said. She was among a group of friends from Messalonskee High School who visit Harvest Hills Farm every fall, authorities said.

Among them was 16-year-old Connor Garland, of Belgrade, who suffered multiple fractures and was being treated at Boston Children’s Hospital, McCausland said. A hospital spokeswoman said he was in fair condition Sunday night. About a half-dozen other injured people remained hospitalized Sunday afternoon but their injuries did not appear life-threatening, Davis said.

Kathy Mathieu, of Oakland, whose son Zachary is a close friend of Garland’s, said Charette and Garland attended the school’s homecoming celebration together last week. She said the community is planning a fundraiser for Charette’s family.

"Everybody is doing everything they can to help this family," Mathieu said. "There are no words to express the sorrow for the parents."

Charette was a member of the girls’ soccer team. Garland is a member of the Central Maine Owls, a 15-and-under baseball team that won the state championship this year.

Messalonskee Principal Jon Moody sent a statement to the school community saying grief counselors would be available at the school this week.

The hay wagon was being pulled by a 1979 Jeep when it crashed, according to the fire marshal’s office. The driver, identified by police as David Brown, 54, of South Paris, was among those injured. Authorities said he underwent surgery late Saturday and was released from the hospital Sunday. Brown is an experienced trucker who has a commercial driver’s license, according to a spokesman for the farm.

Several actors participating in the ride’s scenes assisted the injured riders and likely helped prevent the accident from being even worse, Davis said.

The sprawling farm is set on a forested hill about 25 miles southwest of Augusta, set back from a two-lane road. The owners have been hosting the haunted ride for about five years, farm spokesman Scott Lansley said. The tour’s narrator was among the other 19 people authorities said were injured, he said.

It wasn’t the only fatal accident at a fall festivity over the weekend. In northern New Jersey, a vehicle struck several people near a farm Sunday afternoon, killing one person and injuring several others. The crash happened at a fall festival in Chester, about 40 miles west of Newark.