A tour boat carrying 27 people has sunk off the coast of Vancouver Island, in the Canadian province of British Columbia.

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, owned by Jamie’s Whaling Station & Adventure Centres, was a whale-watching vessel named the MV Leviathan II.

A witness told CBC the boat sank far enough from shore that it could not be seen.

“You could see the smaller boats going back and forth to try and help bring people back to shore,” Rami Touffaha told the CBC. “The waters weren’t choppy so I don’t see what could have caused the boat to sink, but you never know in these waters unfortunately,” he said.

‘A tragic day’

The Leviathan II is a 65-foot cruiser, Jamie’s Whaling Station said on its website. It has three viewing decks – one upper and one lower and one in the back of the boat. It seats 46 passengers comfortably, the website said.

Search coordinators have requested a military helicopter and a fixed wing aircraft to join in the search. Two Canadian Coast Guard vessels have deployed to Tofino, as well as other vessels.

The search continued after nightfall, the coordination center said.

The Transportation Safety Board of Canada will investigate the sinking, it said in a statement.

CNN reached out to the Jamie’s Whaling Station but did not receive immediate response.

CNN’s Joe Sutton contributed to this report.