MUNCIE, Ind. (AP) — Authorities investigating the deaths of a man and two children whose bodies were found in an Indiana home said firefighters detected high carbon monoxide levels inside the residence.

The bodies of the 24-year-old man, a 3-year-old boy and a 21-month-old girl were found Sunday afternoon in the home in the city of Muncie.

Delaware County Coroner Gavin Greene announced on Monday the firefighters’ findings, The Star Press reported. Carbon monoxide is a toxic, odorless gas.

Autopsies were conducted Monday on the three victims, but Greene said the death investigation is ongoing, pending toxicology results and a pathologist’s findings.

Deputy Police Chief Melissa Criswell said city police and fire personnel were also investigating the deaths in Muncie, which is located about 60 miles (100 kilometers) northeast of Indianapolis.