Wolfeboro, NH – Investigators say a car that was left running in a closed garage generated the carbon monoxide that killed a Wolfeboro, N.H., couple last week.

The bodies of 86-year-old John Clarke and 87-year-old Ethel Clarke were found in their home on Aug. 19. The medical examiner determined they died of carbon monoxide poisoning and investigators said no foul play was involved.

WMUR reports fire investigators said they determined that a vehicle was left running in the garage under the house. A central air unit helped circulate the poisonous gas throughout the house.

State Fire Marshal William Degnan said all homes should have carbon monoxide detectors to help prevent accidental deaths.