Five British tourists died on board a whale watching vessel carrying 27 passengers which sank off the coast of British Columbia in western Canada, the Foreign Office has confirmed.

The victims are four men and one woman aged between 18 and 76, with two of them being British ex-pats. All are thought to have died in the water, said the British Columbia Coroner.

The boat, which was operated by Jamie's Whaling Station, had been sailing in the waters off Tofino, a small town on Vancouver Island, before making a mayday call around 5pm yesterday.

One person is still missing as mystery surrounds what caused the boat to capsize and sink.

It is not yet known what caused the boat, named Leviathan II, to sink as locals have said the water was calm at the time, with low wind and good light.

Lt Commander Desmond James, from the Joint Rescue Co-ordination Centre, said the military agency's search had concluded with five people dead, 21 rescued and one person missing.

The Royal Canadian Mounted Police will take over the search for the person who remains missing.

According health officials, 18 people were taken to hospital, many of whom have now been discharged.

Boat Show Avenue's thoughts are with the families of this tragic accident victims.