MILFORD – A state Fish & Game conservation officer said Sunday that the agency, along with local police, are investigating a snowmobile crash that authorities believe occurred when the sled suddenly accelerated and collided with a large rock.

Upon impact, the operator, identified as Nathan Ball, 42, of Milford, and an 11-year-old child were both thrown from the snowmobile, according to Fish & Game Conservation Officer Thomas Houghton.

The child, who wasn’t identified, reportedly lost consciousness for a time. Houghton said the crash occurred at about 12:45 p.m. Saturday on private property, but the address wasn’t provided.

Milford police, firefighters and ambulance personnel responded, and upon arrival were directed to the scene by witnesses.

Also called to the scene was a crew from the town’s Public Works Department to provide equipment to assist first-responders “due to the length and condition of the driveway,” Houghton said.

For reasons still under investigation, the snowmobile “abruptly accelerated in the yard of the private residence,” resulting in the collision with the rock, Houghton said.

Ambulance personnel treated Ball and the child at the scene, and transported both to Elliot Hospital in Manchester. Houghton described the child’s injuries as serious.

Neither Ball nor the child were wearing helmets at the time of the crash. Houghton said excessive speed is believed to be the primary contributing factor to the crash.