The Canadian ship that launched the doomed Titan submersible into the depths of the North Atlantic on Sunday has returned to port in Newfoundland.

“The Polar Prince” pulled up alongside the Canadian Coast Guard building in St. John’s this morning after a journey of about 700 kilometres.

The Titan lost contact with the Polar Prince about an hour and 45 minutes into its descent to the wreck of the Titanic, almost four kilometres below the surface of the sea in what we now know was a catastrophic implosion.

The Titan was owned by the Washington-based company OceanGate Expeditions, and its chief executive officer Stockton Rush was among those who perished on the 7-metre long craft.

The Transportation Safety Board of Canada has said it is launching an investigation into the tragedy.

There was already controversy about the company possibly taking shortcuts in safety procedures, which resulted in one senior staff member leaving the company.