The Canadian-flagged vessel Polar Prince and the privately-operated submersible Titan, which collapsed and killed all five persons on board, were investigated by Canadian officials on Saturday.

The Canadian cargo freighter Polar Prince supported the submersible Titan 325 nautical miles southeast of Cape Race, Newfoundland and Labrador, at the Titanic crash site.

The Transportation Safety Board of Canada (TSB) reported that the support vessel lost touch 1 hour and 45 minutes after the Titan began its descent with five Polar Prince crew members.

The US Coast Guard verified Thursday that the debris recovered near the Titanic wreckage included submersible parts. The five Titan passengers are assumed dead.

The Polar Prince had 17 crew and 24 passengers.

“In accordance with the Canadian Transportation Accident Investigation and Safety Board Act and international agreements, the TSB, as the investigation authority of the flag state of the support vessel involved in the occurrence, will conduct a safety investigation regarding the circumstances of this operation conducted by the Canadian-flagged vessel Polar Prince,” the agency said.

The TSB planned to visit St. John’s, Newfoundland and Labrador, to interview witnesses and investigate the incident.

The Canadian agency said it will work with other agencies in the following days.

Late Thursday, OceanGate Expeditions located Titan submersible debris, confirming all deaths.

Hamish Harding, a millionaire adventurer, and Paul-Henry Nargeolet, a French explorer, were among the five passengers.

Five explorers may never be found.