The bodies of four young people and a family dog were found in a cabin in the town of Byron. Now, officials say they believe the Massachusetts natives died as a result of carbon monoxide poisoning.

According to the BDN, the bodies of 21-year-old Brooke Wakelin, her 18-year-old brother Matthew, 23-year-old Keith Norris, and 22-year-old Deanna Powers were discovered by the Wakelin's father in the family cabin. The group had come to Maine from their homes in Massachusetts, in part, to celebrate Brooke's 22nd birthday, which is today.

Sheriff Wayne Gallant told the BDN that officials believe the young people, and the Wakelin's beagle, died as a result of carbon monoxide poisoning. The rural cabin isn't hooked up for electricity, but there is a generator to provide power. The generator was found in the basement, and officials say it had run through its tank of gasoline. Fumes filled the house while the occupants slept. Gallant says the generator should have been  moved outside.

The State Medical Examiner's office will conduct autopsies to confirm cause of death.