Blue Lake Township, MI – Authorities say carbon monoxide poisoning is believed to have caused the deaths of a married couple found in a western Michigan home.

The Muskegon Chronicle reports the Muskegon County sheriff’s department says family members found Joseph Wayne Jurecki and Barbara Jean Jurecki, both in their 70s, inside the home in Blue Lake Township on Thursday.

Emergency responders detected fumes when they arrived at the home.

Sheriff Dean Roesler says it’s believed that they died at least two days, possible four, before they were discovered. Investigators believe that the couple died of carbon monoxide poisoning due to an improperly ventilated furnace. No foul play is suspected.

The investigation is ongoing.