The Coast Guard and the Self-Defense Forces have expanded the search area for people who went missing in a boat accident off the Shiretoko Peninsula in Japan's northernmost prefecture of Hokkaido.

The 19-ton tour boat, Kazu One, with 26 people on board, went missing on Saturday after making a distress call.

Seven men and three women have been pronounced dead. Coast Guard officials say one child pulled from the waters late Sunday night has also been confirmed dead at a hospital.

The Coast Guard is working to identify the 11 people.

A team of investigators from Japan's transport ministry has begun looking into what caused the accident.

Three marine accident investigators of the Transport Safety Board visited an on-site response center at the Utoro branch of Shari Town on Monday morning.

They told reporters they will gather information from ministry officials at the center before talking to members of a local fisheries association later in the day.

They said they had also talked with officials at a regional Coast Guard station earlier on Sunday.

The team's leader said what they can do now is limited as the rescue operations are underway, but they will do their utmost to collect the necessary information.