At least 10 people are dead and 16 are missing after a sightseeing boat sank Saturday off the Japanese island of Hokkaido, Japan’s coast guard said Sunday.

The tour boat, “Kazu I,” entered choppy waters with high waves and strong winds on Saturday around 1:15 p.m. local time.

There were two children, as well as two crew members, among the 26 aboard the boat, according to the Japan Coast Guard. Of the 10 dead, seven were adult men and three were adult women. 

The coast guard was informed that the boat was flooding and going down Saturday. The average temperature of the water in that area during this time of year is around 37 degrees Fahrenheit due to drift ice.

"Just a few minutes in that sort of water would start clouding your consciousness," an official at a local fishery cooperative told Reuters.

Officials are still continuing to search for the 16 people with patrol boats, aircraft, and helicopters.

The boat left a port in Shari around 10 a.m. on Saturday. Boat tours are common in the area due to the wildlife and mountains. It is believed that the Kazu I was on a three-hour sightseeing voyage around the Shiretoko Peninsula. It was the first tour boat to also operate in the area this season, Kyodo News reported.

According to the coast guard, all the passengers were wearing life jackets and footage showed that orange flotation devices were used.

The coast guard said it is unclear what exactly happened to the boat.

“We will thoroughly investigate what caused this situation and what kind of safety oversight was involved to allow the tour in order to prevent another accident,” Transport Minister Tetsuo Saito told reporters on Sunday.