The Japan Coast Guard suspects a jetfoil ferry boat collided with a whale. A crewmember claims to have spotted a large, white object in the water moments before impact.
The collision occurred on Saturday afternoon while the vessel was travelling from Niigata port to Sado Island. Eighty people were injured, 13 seriously.
Coast guard officials say a roughly 15-centimeter crack is visible on the stern of the vessel and its hydrofoil wing is partially bent. They say the sea was calm and visibility was good at the time of impact.
Another high-speed vessel is thought to have collided with a whale in the same waters in the past.
Coast guard and transport safety inspectors are planning to examine the ferry and try to determine the cause of the accident.