About a dozen killer whales trapped under sea ice in Canada are free after ice shifted.

Residents who feared they would get stuck elsewhere hired a plane to track them down.

The whales' predicament in the frigid waters of Hudson Bay made international headlines.

Locals had been planning a rescue operation with chainsaws and drills before the mammals slipped away.

Tommy Palliser said two hunters from remote Inukjuak village reported that the waters had opened up around the area where the cornered whales had been bobbing frantically for air around a single, truck-sized hole in the ice.

Officials said shifting winds might have pushed the ice away.

"It's certainly good news - that's good news for the whales," said Mr Palliser, a business adviser with the regional government.

But fears remained that the whales might have been trapped elsewhere by the ever-moving ice.

Inukjuak, about 1,500 km north of Montreal, hired an airplane to scan the region for signs of the whales, town manager Johnny Williams said.

"We're quite concerned, that's why we're chartering the plane to find out if we can find them," Williams said, adding that the village of 1,800 likely will pay for the aerial search.

"Even though they're a nuisance, even though they're a killer [of] our [beluga] whales and seals," he said. "They're like humans, they're mammals - alive. They don't need to suffer."

Locals said the whales had been trapped for at least two days.

A recent, sudden drop in temperature may have caught the whales off guard, leaving them trapped.

The cornered animals were first seen last Tuesday and appeared to have less energy by late last night.

Canada's Department of Fisheries and Oceans said government icebreakers were too far from the area to smash the ice to free the whales.

Locals had agreed to try to enlarge the breathing hole in the ice and cut a second opening using chainsaws and drills.

The Department of Fisheries and Oceans issued a statement today saying two scientists were en route to gather information and will monitor the situation. Ice-trapped marine mammals are not unusual in the region.