Officials with the Transportation Safety Board of Canada say they monitored two separate sets of sea trials that simulated the towing of the fishing vessel L'Acadien II by the coast guard icebreaker Sir William Alexander last March.

The sealing vessel flipped over and sank in ice-clogged waters off Cape Breton while it was under tow by the Alexander.

The bodies of three fishermen were found immediately, but one fisherman is still missing and presumed dead.

Witnesses have said the crew aboard the icebreaker weren't properly monitoring the tow as the larger vessel pulled the 12-metre sealing boat onto an ice floe before it overturned and sank.

The board doesn't reveal any findings in the statement, saying only that a report is expected this fall.