SMITHFIELD – Carbon monoxide poisoning killed two men and sickened a third over the weekend, the state Department of Public Safety said Monday.

State police said James Chouinard discovered the bodies about 7 a.m. Monday when he went to the site to work on his son’s house at 652 East Pond Road in this southern Somerset County town.

Dead were 26-year-old Duncan Chouinard and 29-year-old Jason Griffeth, both of Skowhegan. Being treated for CO poisoning is 31-year-old James Staples of Madison.

The State Medical Examiner’s Office said Choinard and Griffeth died of CO poisoning, according to Stephen McCausland, spokesman for the Maine Department of Public Safety.

A portable generator was being used to supply power. It was found on the first floor of the enclosed home and out of gasoline. Investigators think the men were overcome by the fumes either late Saturday night or sometime Sunday, McCausland said. They plan to speak with Staples on what happened once he has recovered.

The 2-story house was being built for the younger Chouinard. The interior work had recently begun.

Griffeth and Staples were friends of the younger Chouinard and apparently were visiting the house over the weekend, McCausland said.

The two bodies were taken to a Skowhegan funeral home where they were examined by retired state Chief Medical Examiner Dr. Henry Ryan.

State Fire Marshal John Dean said, “This tragedy shows the importance of operating generators and other similar equipment outside and the life-saving value of a carbon monoxide detectors, similar to smoke detectors found in most U.S. homes.”