The nine, from the boat that went missing on Saturday with 26 people on board during a cruise off the northern main island of Hokkaido, were found unconscious on Sunday and it was not immediately clear if they had vital signs, a coast guard official told Reuters.
They were taken to hospital, public broadcaster NHK reported.
Drift ice can be seen in area waters as late as March, and water temperatures now would be 2 to 3 degrees Celsius, said an official at a local fishery cooperative.
Authorities were using aircraft and patrol boats, including seven ships, three airplanes and four helicopters from the coast guard, to search for the passengers and crew of the "Kazu I" after it ran into trouble off Shiretoko peninsula, famous for its wildlife and dramatic coastline.
The coast guard heard from the crew on Saturday afternoon that water was flooding the vessel. It was last heard from around two hours 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.
The crew said those on board were wearing life jackets, media reported. There were 24 passengers, two of them children, and two crew members on board.
22°C