Ships have started to return to the harbour after assisting with attempts to recover the Titan submersible which killed five people after it catastrophically imploded.

The Canadian Coast Guard (CCG) confirmed two vessels were en route to St John’s harbour on Friday evening with one remaining on site.

A large crowd gathered at the port on Friday evening to watch the ships return to the harbour, with the Titan’s main support ship, the Polar Prince, due to arrive and dock in the early hours of Saturday morning.

The winding down operation comes as the Transportation Safety Board of Canada (TSB) announced it would be conducting a safety investigation into the fatal implosion of the deep sea vessel.

British adventurer Hamish Harding and father and son Shahzada and Suleman Dawood were killed on board the Titan submersible, alongside the chief executive of the company responsible for the vessel, Stockton Rush, and French national Paul-Henri Nargeolet.

In a statement issued before their ship arrived at the port, the CCG said: “The Canadian Coast Guard offers our sincere condolences to the family and friends of the crew of the Titan for their tragic loss.

“Search and rescue operations have concluded.

“The CCGS Terry Fox and CCGS Ann Harvey are en route to St John’s.

“The CCGS John Cabot will remain on scene and will provide assistance and support to the recovery and salvage operations as requested by Maritime Rescue Coordination Centre Boston.”

The TSB said a team of investigators had been deployed to St John’s in Canada to “gather information, conduct interviews and assess the occurrence”.

In a short statement confirming the investigation, the safety body said: “The TSB is launching an investigation into the fatal occurrence involving the Canadian-flagged vessel Polar Prince and the privately operated submersible Titan.

“In accordance with the Canadian Transportation Accident Investigation and Safety Board Act and international agreements, the TSB… will conduct a safety investigation regarding the circumstances of this operation conducted by the Canadian-flagged vessel Polar Prince.

“A team of TSB investigators is travelling to St John’s, Newfoundland and Labrador to gather information, conduct interviews and assess the occurrence.

“In the coming days, we will co-ordinate our activities with other agencies involved.”

The TSB will not determine civil or criminal liability and conducts investigations for “the advancement of transportation safety”.

The investigation comes after emails emerged from Mr Rush which dismissed safety concerns over the deep-sea vessel.

The exchanges with deep-sea exploration specialist Rob McCallum, reported by the BBC, show the company’s chief executive say he was “tired of industry players who try to use a safety argument to stop innovation”.

Mr McCallum could be seen telling Mr Rush that he was “mirroring that famous cry” of the Titanic’s builders: “She is unsinkable.”

The broadcaster reported the email exchange ended when the company’s lawyers threatened legal action.

The submersible lost contact with the tour operator an hour and 45 minutes into the two-hour descent to the wreckage, with the vessel reported missing eight hours after communication was lost.

In the days that followed the report that Titan had gone missing, the US Coast Guard said the vessel had a depleting oxygen supply that was expected to run out on Thursday.

A report from The Wall Street Journal said the US navy had detected a sound in the search area for the submersible on Sunday that was consistent with an implosion.

The Associated Press, citing a senior military official, reported that the navy passed on the information to the Coast Guard, which continued its search because the data was not considered by the navy to be definitive.