Whale Watching Boat Sinks, Leaving at Least 5 Dead including men aged 18 and 76

At least five people are dead after a whale watching boat capsized off the coast of Canada on Sunday.

Authorities in Canada revealed Monday afternoon that four of the victims in Sunday's whale boat capsizing were men while the fourth was a woman and included with the victims was a 76-year-old and a man still in his teens.

All the victims were U.K. nationals. A sixth person remained missing Monday.

The Leviathan II was carrying 27 people when it sent out a distress call near Tofino on Vancouver Island just before 4 p.m. on Sunday.

A rescue helicopter and boat made it to the scene within 30 minutes, BBC Canada reports. Twenty-one passengers were rescued.

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A spokesman for the Vancouver Island health authority said 18 of those rescued were taken to a hospital for treatment and all were in stable condition, the Guardian reports.

British Foreign Secretary Philip Hammond first revealed on Monday that all five confirmed victims were British -- two were U.K. nationals living in Canada while three were tourists.

Their identities were not immediately known.

Hammond said his thoughts were "with the family and friends of all those affected by this terrible accident."

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A sixth person was still missing as increasing darkness forced rescuers to call off the search on Sunday.

On Monday, the sixth person remained missing and the case was turned over to Royal Canadian Mounted Police.

It also remained unclear Monday what caused the ship to capsize on a sunny day in calm seas.

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