Five British nationals died on board a whale watching boat that sank off western Canada, the UK's Foreign Secretary has confirmed.

One person remains missing after yesterday's tragedy off Tofino, British Columbia. Their nationality is not yet known.

In total, 27 passengers were on board the vessel when it made a mayday call on Sunday afternoon - 21 of whom were rescued.

Consular staff in British Columbia are supporting the family members of those who died.

Investigators are now trying to determine what caused the boat to sink on what was a calm, clear and sunny day near Vancouver Island - a popular destination for tourists and whale watchers.

Some survivors have been discharged after being briefly treated in hospital.

The vessel, named the Leviathan II, was operated by Jamie's Whaling Station and Adventure Centres.

In a statement late last night, the company wrote: "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 cooperating with investigators to determine exactly what happened.

"In the meantime, we want to extend our most sincere thank you to the first responders, rescue personnel, and everyone from Tofino and the local First Nations communities who assisted with the response efforts."