Rock Springs, WY – Carbon monoxide poisoning is being blamed in the deaths of a Utah father and son who were camping in an ice fishing hut at Flaming Gorge Reservoir in southwest Wyoming.

Sweetwater County sheriff’s Col. Rick Hawkins said 58-year-old Steven McConnell and his 17-year-old son, Matthew, of Stansbury Park, were found unresponsive by companions who tried to wake them around 9 a.m. Monday.

Emergency responders confirmed the deaths, The Salt Lake Tribune reported.

The source of the toxic gas apparently was a lit propane heater found inside the ice-fishing hut the two slept in, the sheriff’s department said.

The father and son were camping with a group over the weekend in the Big Firehole area.

Members of the group told investigators that the McConnells were sleeping on cots and went to bed at about 1 a.m. Monday. The group planned to break camp later that morning, but when they tried to wake the McConnells around 9 a.m., both were unresponsive.

Laurie McConnell said her father and brother were longtime sportsmen and that her father was always careful.

Hawkins said no foul play is suspected.