Springdale, AR – Authorities say no foul play is suspected in the deaths of a father and his son found dead in a northwest Arkansas auto shop last week.

Springdale police say emergency responders found the bodies of 35-year-old Travis Walls and his adolescent son Friday at the shop after they were reported missing for 12 hours. The Northwest Arkansas Democrat-Gazette reports that the pair may have died from emissions that came from a generator.

Springdale Fire Department Capt. Dustin McDonald says firefighters detected high levels of carbon monoxide inside the shop. Both bodies were sent to the state Crime Laboratory for autopsies.