(CNN) -- A group of killer whales that had been trapped beneath ice and in danger of dying in Canada's Hudson Bay have not been seen Thursday, authorities said.
Inukjuak Town Manager Johnny Williams said shifting wind patterns overnight allowed the ice to break as the 11 whales struggled to stay alive.
The orcas had been confined to a space of about 30 feet by 30 feet. They were last seen Wednesday afternoon, according to Williams.
"The plane flew over where the whales ought to be, but they didn't find them," Williams told CNN, indicating the whales were no longer near the town.
Williams said emergency crews redrew plans for deployment.
"We're in a stand-down mode, but we're still ready to go if needed," said Ray Lee, the president of Kasco Marine, which helped save whales in a celebrated rescue in 1988.
In that incident, three gray whales were trapped in ice near Barrow, Alaska. The story made national news for several nights and was the inspiration for the 2012 film "Big Miracle."
Two of the three whales made it to open water after rescuers used chainsaws and deicers from a Wisconsin company to create more breathing holes, and a Soviet icebreaker cleared a path through the thickest ice.
-- CNN's Elwyn Lopez contributed to this report.
™ & © 2013 Cable News Network, Inc., a Time Warner Company. All rights reserved.