A pod of killer whales that was trapped in drift ice off Japan’s northern main island of Hokkaido, prompting concern from environmental groups, has apparently safely escaped, officials said Wednesday.

The killer whales, also known as orcas, were initially spotted by a local fisherman who reported them to officials in the nearby town of Rausu on the northeastern coast of Hokkaido on Tuesday morning. After analyzing drone footage filmed by a conservationist group, officials counted 13 killer whales there.