WALKER, Minn. (AP) - Cass County authorities say a man died after apparently suffering from carbon monoxide poisoning in an ice fishing house on Leech Lake.

Reports say emergency responders and deputies found one man dead and three others sick in the fish house on Walker Bay on Sunday afternoon.

Sheriff Tom Burch says the fish house was a converted camper trailer, and the initial investigation indicates that the propane heaters in the shelter were not ventilated.

One of the surviving men was taken to a Park Rapids hospital, then transferred to a Twin Cities hospital, while the two others were treated at the scene.

Names of the men have not yet been released because family members are still being notified. An autopsy is scheduled for the man who died.