An ice-fishing house blew up over the weekend on Upper Red Lake, injuring four people, authorities said.

The Beltrami County Sheriff's Office received a call about 12:30 p.m. on Saturdayabout an explosion in Waskish Township, on the northeast end of the lake, more than 2 miles from shore.

According to Sheriff Ernie Beitel, four people were in the fish house, using a propane heater, when they heard a hissing noise. After they turned off the valve on the tank, a fireball filled the ice house.

The ice house, a wheeled structure with a rigid frame, was heavily damaged in the explosion. Two men and two women were flown by helicopter to regional medical facilities with burn-related injuries. Their conditions have not been released.