More than 80 people have been injured after a ferry collided with what is thought to have been a whale off a Japanese island.

The accident happened off Sado Island, the Kyodo News agency reported.

Five people were seriously injured and a 6in crack was later found at the ferry’s stern.

Firefighters prepare to taken injured passengers to a hospital at a port in Sado city (Kyodo News via AP)

Ferry operator Sado Steam Ship Co said the jetfoil ferry still reached its intended destination on the island, located off the west coast of Japan’s main island of Honshu.

The ferry, which departed from Honshu’s Niigata Port, was carrying 121 passengers and four crew members.

The cause of the accident is under investigation by coast guard officials, who said the ferry may have struck a marine animal.