The winter’s late ice fishing season turned tragic Sunday when one angler died and another was hospitalized after carbon monoxide poisoned them in a fish house on Leech Lake in northern Minnesota.

On Tuesday, the Cass County Sheriff’s Office identified the man who died as 34-year-old Jared Nels Johnson, of Akeley, Minn.

Propane heaters in the fish house, converted from a camper trailer, were not ventilated, leading to a buildup of the gas, Cass County Sheriff Tom Burch said by phone Monday. He urged anglers to “make sure your places are ventilated” and watch for symptoms of carbon monoxide poisoning, which can mirror the flu.

“If you’re feeling sick — upset stomach, dizziness — you need to get out of there and call for help right away,” Burch said.

Two other men in the fish house, on Walker Bay on Leech Lake’s west side, were treated for carbon monoxide poisoning and released, according to the sheriff’s office.

Authorities were alerted to the trouble after one of the four men called for help about 4:30 p.m. Sunday, Burch said. Deputies and emergency medical responders arrived at the fish house and found one man dead. One of the survivors was sent to St. Joseph’s Hospital in Park Rapids, then transferred to Hennepin County Medical Center.

Carbon monoxide is odorless and tasteless, so having a working detector is key, said State Fire Marshal Bruce West. “Even with a fish house, they could have a battery-operated carbon monoxide alarm,” he said.

Anglers should follow manufacturers’ specifications, making sure that heating units are properly vented and those vents are clear of snow, he added.

“If you have some type of heater in there that’s not vented to the outside,” West said, “you’re basically getting a good amount of carbon monoxide into the fish house.”

Carbon monoxide emergencies peak during cold months, when furnaces and fireplaces are working hard and windows are shut tight. The Minnesota Department of Health recommends that ice fishing houses with heating equipment have a working alarm and a window cracked.

The Cass County Sheriff’s Office doesn’t track carbon monoxide incidents in the area’s fish houses, Burch said.

But, he added, “It’s not as uncommon as you would think. Unfortunately in this case, someone lost their life.”