As many as four people are feared dead after a float plane crashed into the water off Vancouver Island on Saturday.

Authorities say the plane, a Cessna 185, crashed upside down near the Ahousat First Nation, located just north of Tofino, at about 12:15 p.m.

Witnesses say the aircraft remained afloat for about 10 minutes before sinking into water approximately 50 feet deep.

A pilot and three passengers, two women and one man, are believed to have been on board.

Rescue coordinator Victor Weston said diving crews were unable to find any sign of the plane or its passengers, and called off their search early Saturday night.

"We have not recovered or rescued anyone," Weston said.

"Our air assets and marine assets are back at their bases."

Vancouver Island Mounties will continue to search the water on Sunday, Weston said.

The plane belonged to Atleo River Air Service, based in Tofino. It was reportedly headed to Ahousat on a 12-minute flight.

No distress calls were picked up prior to the crash.