At least 10 orcas that were seen trapped by sea ice off the coast of northern Japan on Tuesday appeared to have escaped, local officials in the nearest town said Wednesday.

Drone video released by local wildlife organization Wildlife Pro showed the pod of killer whales struggling with their heads above the frozen waters off Hokkaido, Japan.

Local officials told public broadcaster NHK the coast guard had been unable to rescue the whales, which were stuck a little over half a mile from the coast, on Tuesday because the surrounding ice was too thick. By Wednesday morning, however, they could no longer be seen in the spot.

"As the gap in the drift ice started to open, it's likely they escaped," an official in the town of Rausu was quoted as saying by Japan's Kyoto news agency. They said the animals could no longer be spotted with binoculars from the shore.

Rausu is situated on Hokkaido's Shiretoko Peninsula, which is designated a World Natural Heritage Site by the United Nations.

About 10 orcas died in 2005 after getting stuck in drift ice in the same area, according to Kyoto.