Story highlights Twenty-seven people were on board when the boat sank

It's not immediately clear how many survived

The boat was reportedly a whale-watching vessel

(CNN) Rescue workers scoured the waters off the coast of Tofino, in the Canadian province of British Columbia, on Sunday after a tour boat carrying 27 people sunk, authorities said.

At least four people died, according to the Joint Rescue Co-ordination Centre. It wasn't immediately clear how many people survived.

"There are fatalities involved, and survivors," the Joint Rescue Co-ordination Centre said in an earlier recorded message.

"We're also conducting a search to confirm that we've recovered everybody," the message said.

The boat was a whale-watching vessel, according to the Canadian Broadcasting Corporation.

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