FARMINGTON — A Wilton mother and her son sustained serious injuries Wednesday when the ATV they were riding on went off a bridge over Hardy Brook on the Whistle Stop Trail, Mark Latti, spokesman for Maine Department of Inland Fisheries and Wildlife, said.

Kerri Stone, 26, and her son, Ashton, 6, were traveling with two other ATVs.

Stone apparently lost control of the machine, which went off the side of the bridge and down an embankment with about a 23-foot drop.

“Both received serious injuries,” Latti said.

Ashton was flown by a LifeFlight medical helicopter to Maine Medical Center in Portland, he said. His mother was taken by a NorthStar EMS ambulance to the same hospital.

Maine wardens Kris MacCabe, Harry Wiegman and Dan Christianson responded to the scene. Farmington Fire Rescue Department and NorthStar medics responded to the report of an accident at about 10:30 a.m.

The accident remains under investigation, Latti said.

Whistle Stop Trail, an old railroad bed, is about 14 miles long and runs from Jay to West Farmington. The bridge over Hardy Brook is about 100 yards off Red Schoolhouse, which runs behind Walmart. The road is off U.S. Route 2/state Route 4.