The four adults were found in a home in Wakefield on Wednesday afternoon, officials said.
Four people were found dead in a New Hampshire home on Christmas Day of suspected carbon monoxide poisoning, officials said.
The four adults were found dead in the home in Wakefield around 4:20 p.m. after authorities were contacted to do a welfare check, the state fire marshal and police said.
"While the investigation remains active and ongoing, at this time, investigators believe the victims died as a result of carbon monoxide poisoning," the fire marshal and chiefs of the Wakefield police and Wakefield Fire Rescue said in a news release.
More than 400 people die each year in the United States from carbon monoxide poisoning not linked to fires, the Centers for Disease Control and Prevention say on its website.
The colorless and odorless gas can come from electricity generators, furnaces, exhaust from vehicles and other sources.
New Hampshire State Fire Marshal Sean P. Toomey in Wednesday's statement about the incident stressed the importance of having working carbon monoxide alarms in homes.
Wakefield is a town of around 5,000 in the eastern part of New Hampshire, near the Maine border.