Japan's coast guard used aircraft and patrol boats on Saturday to search for a tour boat with 26 people on board after it sent word it was in trouble off the northern island of Hokkaido, a coast guard official said.
The coast guard heard from the crew of the "Kazu I" at around 1:15 p.m. (0415 GMT) that water was flooding into the vessel, the official said. The boat had been on a sightseeing cruise around the Shiretoko Peninsula, which is famous for its wildlife and dramatic coastline.
The ship was last heard from at around 3 p.m. when it contacted its operating company to say it was keeling at a 30-degree angle, news agency Kyodo reported. The crew said those on board were wearing life jackets, public broadcaster NHK said.
There were 24 passengers including two children on board and two crew members, the official said.
No one answered calls to the office of the company that runs the Kazu I's sightseeing tours.
The coast guard had dispatched five patrol boats and two aircraft and was still searching late on Saturday, the official said.
Authorities had requested help from Japan's self-defense forces, media said, while Prime Minister Fumio Kishida gave instructions to use all available means in the search, Kyodo said, citing a person familiar with the matter.
Kishida will cut short his visit to the southern prefecture of Kumamoto, where he was attending the Asia-Pacific Water Summit, and return to Tokyo because of the issue, Kyodo said.
The government also set up a task force to deal with it.
The boat was believed to have been near the Kashinu Falls, a popular sightseeing spot for its natural beauty, when it got into difficulty.
The ship holds up to 65 people and tours around the Shiretoko area usually last around three hours, according to the tour company's website.
It left Utoro port around 10 a.m. on Saturday and was expected to return by 1 p.m., NHK said. Waves had been high and fishing boats in the area had returned to the port by mid-morning.