Open throttles were blamed for two unrelated snowmobile accidents Sunday.

In Northport, a snowsled operator and a 6-year-old boy were injured Sunday morning when the throttle on their machine apparently stuck in the open position and they were catapulted onto the hood of a parked pickup truck.

In northern Somerset County, a 9-year-old Sabattus boy was seriously injured Sunday afternoon when the snowmobile he was on took off unexpectedly during a gasoline stop, traveled 140 feet and hit a tree.

The Maine Warden Service was investigating both accidents.

In the Northport case, Oakley Shedd, 64, and Marlon Hansen, 6, both of Hart Road, were taken to area hospitals after the 11:30 a.m. accident. Shedd suffered broken ribs and facial lacerations and Hansen broke his nose and lost teeth, according to authorities.

Neither was wearing a safety helmet.

Waldo County Sheriff’s Deputy Merl Reed said Shedd, with Hansen in front, was riding down a snowmobile trail at the end of Hart Road when the throttle became stuck. The machine’s engine raced and Shedd was unable to slow it down.

A snowbank and metal gate at the end of the trail acted as a ramp, so the speeding snowmobile was launched into the air and landed on the hood of Shedd’s truck. Both riders were thrown over the truck and landed on the gravel road.

Neighborhood children who witnessed the accident said the snowmobile was traveling at a high rate of speed when it hit the gate. Shedd’s son, who witnessed the wreck, stayed by his father’s side until help arrived.

The 6-year-old Hansen ran to his house a few yards down the road, and his mother called 911 for help. Northport Fire Department and Belfast Ambulance personnel responded to the call and were on the scene within minutes.

In the Somerset County accident, in an area known as Pittston Farms, 9-year-old Christopher Ames Jr. was flown by helicopter to Eastern Maine Medical Center in Bangor after the snowmobile he was on hit a tree.

His condition was not immediately known Sunday night.

Sgt. Roger Guay of the Maine Warden Service said the accident occurred about 1:50 p.m.

The boy’s father, Christopher Ames Sr., 31, had filled the snowmobile with gasoline at a station in the tiny community on the western edge of Seboomook Lake. Guay said the boy, who was wearing a helmet, was sitting on the machine while his father gassed it up.

Before getting onto the snowmobile, the father started the machine, according to the warden. The throttle engaged and the sled took off. It traveled at a high rate of speed for about 140 feet, then hit a tree, according to the warden.

Guay said the snowmobile would be examined to try to determine what caused the throttle to open as the machine was started.

He said several accidents involving stuck throttles have occurred each season, but he described Sunday’s accident as one of the more severe accidents.