Whale-watching boat with 27 on board fatally sinks off coast of British Columbia

A whale-watching boat has sunk off the coast of Tofino, British Columbia with at least four of the 27 people on board being reported dead.

A critical care transport crew has airlifted at least two people to facilities outside Tofino, which has a small hospital with only 10 acute care beds.

Paramedics say survivors are being warmed; at least five people were in the icy waters est of Vargas Island for a significant amount of time, CBC News reports.

It is not yet clear whether all the passengers have been accounted for.

Also unknown is precisely why the boat sank - witness Rami Touffaha, who owns a local charter company, said conditions were not adverse.

"The waters weren't choppy so I don't see what could have caused the boat to sink, but you never know in these waters unfortunately," he told CBC.

"There was about three ambulances down at the dockl. I think that's pretty much all of Tofino's resources.

"You could see the smaller boats going back and forth to try and help bring people back to shore," he said, explaining that the boat was visible from the shore.

This is a breaking news article. More information will be added as it comes to hand.