The country’s transportation safety board is already looking into the incident which occurred on Sunday and have begun questioning some of the 21 survivors, including three crew members.

They believe that the Leviathan II’s sinking of the coast of Tofino happened as passengers gathered on one-side of the boat’s top deck to watch sea lions and so altering the boat’s balance when the wave struck, The Guardian has reported.

The board’s director of marine investigations Marc-André Poisson said: “We know that most passengers were on the top deck on the port side.

“This would have raised the centre of gravity, affecting the vessel’s stability. We also know that the sea conditions were such that a wave approached from the starboard quarter ... We know that the vessel broached and then capsized.”

However, Poisson said the enquiry was still at an early stage and a full report into the incident will take months to conclude.

He added: “None of this preliminary information should be used in isolation to draw any conclusions at this point.”

A British Columbia coroner also said yesterday that the five people killed in the incident had been standing on the top deck of the boat when it capsized.

All the known dead are British while the search continues for the only passenger unaccounted for, an Australian tourist.