Woodstock Township, MI – Three men were found dead inside a travel trailer Saturday at a country music festival in southern Michigan in what police believe is a case of carbon monoxide exposure, officials said.

Two other men inside the trailer were taken to a hospital after first responders found them unresponsive and performed CPR at the scene, the Lenawee County Sheriff’s Office said in a news release.

The pair were in critical condition and being treated for acute carbon monoxide poisoning, police said.

“The caller was a friend of the five males and became concerned when he had not heard from them,” police said.

“First responders stress the importance of keeping generators away from camping areas, tents, travel trailers, etc. as well as exhaust fumes from running vehicles,” police said.

Woodstock Township is about 80 miles west of Detroit.