DELAWARE, Ohio (AP) — Authorities believe a tankless water heater likely caused a carbon monoxide leak that killed a family of four at a home in Ohio.

Genoa Township authorities found 50-year-old Richard Reitter III, 49-year-old Jennifer Reitter, and their children, 15-year-old Richard Reitter IV and 13-year-old Grace Reitter dead in their home May 2. Their three dogs also were dead.

Township police say the last known contact with the family was April 29 when they all complained of illness.

Investigators say a forensic engineering company tested the water heater and found it emitted high levels of carbon monoxide. Police said determining what caused the leak would require more testing.

No carbon monoxide detectors were found in the home.

Genoa Township is roughly 20 miles north of downtown Columbus in Delaware County.