The Japan Coast Guard says a sightseeing boat that remains missing off the coast of the country's northern prefecture of Hokkaido reported an engine failure before losing contact. A search is underway for the 26 people on board.

Coast Guard officers say the boat sent a distress call on Saturday afternoon during its tour around the Shiretoko Peninsula, a UNESCO World Heritage site.

They say 24 passengers, including two children, and two crewmembers were on board the ship.

The crew told the officials that the ship was taking on water and listing at an angle of about 30 degrees and that it could not move on its own as its engine had stopped.

The Coast Guard sent six patrol ships and four planes to look for the boat "KAZU I." The Air Self-Defense Force also dispatched a search-and-rescue aircraft. But the boat has not been located yet.

The operating company says the boat left a port on the peninsula on Saturday morning for a three-hour excursion and was supposed to return to the port.

Meteorological Agency officials say waves in the area were up to three meters high at the time the boat issued the distress call.

The Coast Guard says the boat ran aground last June right after leaving the same port. None of the 23 people on board were injured and the ship was able to return to the port.

Prime Minister Kishida Fumio says he instructed his officials to do everything possible to rescue the missing. And he is sending the transport minister to Hokkaido to lead the search and rescue mission.