The 10 people found by rescue workers on Sunday after a tour boat went missing in frigid waters off Japan’s northernmost island have been confirmed dead, the coast guard said.

Authorities continued their search with patrol boats, aircraft, and helicopters for the remaining 16 people who had been on board the “Kazu I” when it ran into trouble on Saturday off the Shiretoko peninsula on the northern island of Hokkaido.

Nine of those found were either in the water or on nearby rocks, the coast guard said. There were 24 passengers, including two children, and two crew members on board. The two children were still unaccounted for.

Drift ice can be seen in the sea around the area as late as March, and water temperatures would be around 2 to 3 degrees Celsius (36-37 Fahrenheit) at this time of year, an official at a local fishery cooperative told Reuters.

“Just a few minutes in that sort of water would start clouding your consciousness,” he said.

The area is famous for its wildlife and dramatic mountains and boats bring tourists along the coast to spot brown bears.

The coast guard heard from the crew on Saturday afternoon that water was flooding the vessel. It was heard from around an hour later when it contacted its operating company to say it was keeling at a 30-degree angle, Kyodo news reported.

The coast guard said it was not clear what had happened to the boat. No one was available for comment at the company that operated the Kazu I.

High waves and strong winds had been observed around noon on Saturday, Kyodo said.

The boat was the first tour boat to operate in the area this season, the news agency said.

It collided with a floating object in May last year, injuring three people, and ran aground in shallow water shortly after leaving the port in June, Kyodo said.