Five people died after a whale-watching vessel sank off the coast of Tofino, British Columbia last Sunday.

21 passengers were successfully rescued and admitted to Tofino General Hospital and other hospitals. One passenger was reported to be missing after search and rescue efforts were capped late Sunday evening.  

A total of 27 passengers were aboard MV Leviathan II. They were on Tofino -- a popular whale-watching destination - in hopes to see humpback and Pacific Gray whales.

Owned by Jamie's Whaling Station & Adventure Centres, the Leviathan II is a 65-foot cruiser, with three viewing desks. It has a 46-seater capacity with enough space for each passenger to be seated comfortably.

A statement from the touring company's owner, Jamie Bray, was released through their website. It stated: 'It has been a tragic day. Our entire team is heartbroken over this incident and our hearts go out to the families, friends and loved ones of everyone involved. We are doing everything we can to assist our passengers and staff through this difficult time'.

According to Joint Rescue Co-ordination Centre, the company was also involved in another fatal whale-watching incident way back 1998 where a boat operator and a passenger were tossed overboard and drowned.

Rami Touffaha, a witness, told the Canadian Broadcasting Corporation that the waters weren't rough when the tour boat sank. However, the witness said that it sank far enough from shore.

"You could see the smaller boats going back and forth to try and help bring people back to shore," Rami Touffaha said.

On the other hand, John Forde, a tour operator, said he arrived at the area and found the boat nearly submerged. He was on a boat excursion with tourists when the news broke out. 'It was quite close to the rocks and you could still see part of the vessel above water', he said.

Investigations spearhead by Transportation Safety Board of Canada are ongoing. It aims to find the cause behind the boat's sinking.