TOKYO (AFP, REUTERS) - Japan’s coast guard dispatched patrol ships and aircraft on Saturday (April 23) to search for a sightseeing boat carrying 26 people that sent a call warning it was sinking off the north coast, the coastguard and local media said.

The Kazu 1 was sailing off the northern tip of Japan’s Hokkaido prefecture when it issued the signal, Transport Minister Tetsuo Saito told reporters in a late-night press conference.

The crew reported “that the bow of the vessel was flooded just off the coast of Shiretoko Peninsula and that the vessel was sinking... asking for rescue assistance,” he said.

“There were two crew members and 24 passengers on board, all of whom were wearing lifejackets,” Saito added.

The vessel was sailing in the cold and rough waters off the northern tip of Hokkaido prefecture, national broadcaster NHK said.

As of 9.30pm local time, some eight hours after the initial distress call, officials said the search was ongoing.

The distress call said the vessel was “tilting about 30 degrees”, NHK said.

The coastguard then reportedly lost contact with the vessel, and search helicopters arrived in the area around four hours after the distress signal was sent.

The Shiretoko Peninsula is a world heritage site designated by Unesco in 2005 and is known for its unique wildlife, including the endangered Steller sea lion, as well as migratory birds and brown bears.

No one answered calls to the office of the company that runs the Kazu 1 sightseeing tours. According to its homepage, the boat holds 65 people.

Tours around the Shiretoko area usually last around three hours, according to the tour company.

The boat left the Utoro port around 10am yesterday, and was expected to return to port by 1pm, NHK said. Waves had been high and fishing boats in the area had returned to the port by mid-morning.

The boat went missing in waters where temperatures currently hover around zero degrees Celsius at night.

Local media reported the daytime water temperature in the area was around two to three degree Celsius, and that some local fishing boats had returned to port early because of high waves and strong wind.

Japan’s coastguard have been involved in a variety of search and rescue missions around the archipelago, including the successful discovery last November of a 69-year-old man who spent 22 hours drifting in open water off southwestern Kagoshima.