Carbon monoxide poisoning is suspected in the deaths of four people in a home in a tiny eastern North Dakota community, authorities said Tuesday.

The deaths occurred late Sunday in the house just outside of Blanchard, a township roughly halfway between Grand Forks and Fargo, according to the Traill County Sheriff's Office.

The bodies were found in the basement of the house just south of Hwy. 200, the Sheriff's Office said.

Four others in the home, a woman in the basement and three children on upper floors, were rescued and hospitalized in Fargo, the Sheriff's Office added.

"It appears … that a propane-fueled tankless water heater, which was being used to fill a large swimming pool, was improperly vented, causing carbon monoxide to build up inside the home," a statement from the Sheriff's Office read.

The dead were identified as homeowner Ross Matejcek, 53; Ricky Fisher, 27, of Blanchard; Margaret Fisher, 24, of Portland, N.D.; and Jabin Newmes, 6, of Portland.

The woman who survived is Bonnie Fisher, 45, of Blanchard; the surviving children are ages 4 and 2 years old, and 8 months old. The identities of the three surviving children and their conditions have yet to be released. Bonnie Fisher was in good condition late Tuesday morning.

Bonnie Fisher is Matejcek's girlfriend. Ricky and Margaret Fisher were Bonnie's children, and Jabin was Bonnie's grandson. They all lived in the home, a relative told the Grand Forks Herald.

The Sheriff's Office said in its statement that it was first alerted to the "unknown situation with multiple victims" by a 911 call shortly after 10:15 p.m. Sunday.

"Contact was lost with the caller before more information could be" gathered, the statement continued.

Emergency responders from various communities arrived to find "several people inside the residence in varying degrees of distress," the statement added.

Blanchard had a population of 26 as of 2010, according to the U.S. census. Its claim to fame for many years has been the nearby KVLY-TV transmission mast, which at 2,063 feet was the world's tallest structure until a skyscraper in the United Arab Emirates overtook it in 2010.

Paul Walsh • 612-673-4482