MINNEAPOLIS (WCCO) — The Cass County Sheriff’s Office says one fisherman is dead after an incident on Leech Lake.

On Sunday at 4:37 p.m., deputies responded to the report of a medical emergency at a fish house on Walker Bay of Leech Lake.

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Upon arrival, EMS and deputies located four men in a camper trailer, which had been converted to a fish house. The men were experiencing symptoms believed to be carbon monoxide poisoning.

One of the men, later identified as 34-year-old Jared Nels Johnson, of Akeley, was dead. Another man was taken to St. Joseph’s Hospital in Park Rapids and subsequently taken to the Hennepin County Medical Center.

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The other two men were treated on scene and released.

According to the sheriff’s office, propane devices used to heat the structure were not ventilated and led to unsafe levels of carbon monoxide inside the structure.

An autopsy is scheduled for the deceased victim at the Ramsey County Medical Examiner’s Office.

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The three other victims’ identities have not been released.