A whale-watching boat containing 27 passengers sank in the Pacific ocean off the coast of British Columbia on Sunday, Oct.25 killing five British nationals, while one unidentified person is still missing.

The whale-watching boat, which sailed with three crew members capsized midday on Sunday. The Canadian military, Coast Guard, fishermen and mariners from a nearby community immediately launched a rescue team to find the victims. It was confirmed that five people were dead, while one is missing, who's believed to have drowned under the water. The rest of the 21 passengers were declared safe, according to Reuters.

"My thoughts are with the family and friends of all those affected by this terrible accident," UK Foreign Secretary Philip Hammond said in a statement.

According to the reports, the casualties of the whale-watching boat, MV Leviathan II, operated by Jamie's Whaling Station that sank includes four men and a woman, whose age falls between 18 to 76.  All the dead victims were passengers and not members of the crew.

"It was quite close to the rocks and you could still see part of the vessel above water," said John Forde, who owns the Tofino Whale Centre, who has helped in the rescue operations. "There was a lot of injured and hypothermic people being brought in Ahousaht water taxis, at least a dozen boats out there if not more."

When the whale-watching boat sank, the 18 survivors were immediately rushed to a nearby hospital after they were located in the water.  Some of the victims were warmed and given first aid in some of the local residences with the help of the paramedics.  A critical care transport crew arrived and flew two patients to a care facility outside Tofino, CBC reports.

Meanwhile, it is the first accident for the Canadian whale-watching boat company. In 1998, another ship sank while on an excursion. The tragic sinking of the ship led to two deaths. The operator and one of the passengers died while four other were drowned. There is no news as of this writing if the last person who has gone missing was already found.