Investigators say ice clogging up the fuel system was a key problem leading to the crash of a light plane near Kisbey, Sask. on the Easter weekend.

Four adults and two children were on board as the Piper Cherokee 6 crashed in a snowy field Sunday morning. No one died, but one person — the pilot — suffered serious injuries.

Peter Hildebrand, regional operations manager for the Transportation Safety Board, said plane's engine failed after the pilot switched from one fuel tank to another.

"We found in the right outboard tank, a considerable amount of ice which indicated there'd been water in there at some time," Hildebrand said, adding there was ice "in the fuel lines leading to the fuel selector…and in the line leading to the engine."

Investigators have taken the plane apart and say the ice would have prevented fuel in the second tank from getting to the engine.

Water might have entered the fuel tanks if the caps on top of the wing had not been sealed properly, or along with the fuel when the plane was loaded, Hildebrand said.

Investigators said the seals on the fuel caps did appear to be weathered, but could not conclude if they were to blame. The water could also have come from condensation, although Hildebrand said the amount involved was more than he would have expected to see from condensation alone.

Pilots are trained to check for water in the fuel before taking a flight, but, "the amount here was more than one would normally be able to drain away just easily, for example through the fuel bowl, so it sort of overwhelmed the system," Hildebrand said.

The pilot did take steps to drain the water, Hildebrand said, but "the system is really designed to drain smaller quantities of it. Once you have a lot of water in the tank, it's difficult to get it all out."

The investigation is almost complete at this point, according to the TSB.

Kisbey is about 150 kilometres southeast of Regina.