CASCO — Two snowmobilers were injured, one critically, in an accident on Thomas Pond Sunday.

Thomas Hartley, 47, of Casco, and Patricia Butler, 41, of Naples, were ejected from the snowmobile they were riding together on the pond around 12:05 p.m. when they lost control and crashed into the shoreline, according to a Department of Inland Fisheries and Wildlife press release.

After being thrown off the snowmobile, Hartley hit his head on an aluminum boat launch, Game Warden Pete Herring said. Hartley was brought to Maine Medical Center with a broken neck, broken collarbone and head lacerations. He was in critical condition as of 8 p.m. Sunday, according to the press release.

The second passenger, Patricia Butler, suffered bruises on her upper body.

Neither rider was wearing a helmet at the time of the accident.

The Department of Inland Fisheries and Wildlife issued Hartley summonses for operating under the influence and refusing to submit to a blood alcohol test, according to the press release.

Two fishermen who witnessed the accident said that Hartley was sitting behind Butler but was driving the snowmobile when the sled tipped over.

Game wardens continue to investigate the incident, DIFW spokeswoman Deborah Turcotte said.