Pelagic Research Services set out a timeline of its response to the Titan emergency in a news conference this evening.

"We were always conscious of the crew of the Titan," Ed Cassano, CEO at the company, told the media, as he described its efforts to find the submersible.

"Plain and simple, we were focused on rescue," he added.

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However, when Pelagic's vessel arrived at the site of the Titanic wreck, hopes of a rescue did not last long, Mr Cassano explained.

"Shortly after arriving on the seafloor, we discovered the debris of the Titan submersible...by 12 o'clock, a rescue turned into a recovery," he said.

Choking back tears while speaking to reporters, Mr Cassano apologised and said the team were processing "a lot of emotions".

He asked everyone to recognise the "seriousness of the event" and to "respect the range of emotions" felt by those involved.

Mr Cassano said his team were the "primary asset" to "effect rescue" as part of a fleet of ships.

He said: "Our plan of rescue was to - immediately upon finding Titan - to latch onto her as quickly as possible and begin recovery."

Apparently overwhelmed by the tragedy, he added: "It was wild…"

The US Coast Guard revealed on Thursday that presumed human remains had been recovered after debris from the craft was brought ashore.

The nature and extent of the possible remains recovered from the site were not specified.

The five men on board the OceanGate submersible were killed after Titan, which is believed to have suffered a catastrophic implosion, was on its voyage to the wreck of the Titanic.

The 21ft vessel is believed to have imploded on 18 June as it made its descent, with debris located about 12,500ft underwater and roughly 1,600ft from the Titanic on the floor of the Atlantic Ocean.

British father and 19-year-old son Shahzada and Suleman Dawood were killed on board the vessel, along with British billionaire Hamish Harding.

Two other people on board - OceanGate Expeditions' chief executive, Stockton Rush, and French sub pilot Paul-Henri Nargeolet - also died.

The implosion of the Titan has raised questions about the safety of private undersea exploration operations.

Royal Canadian Mounted Police previously said they are looking into the five deaths.

Meanwhile, safety investigators from the Transportation Safety Board (TSB) of Canada made inquiries on Titan's main support ship, the Polar Prince, after it docked in St John's harbour on Saturday.

An extensive search and rescue operation - involving vessels on the water, aircraft and remotely operated vehicles (ROVS) underwater - was launched after Titan lost communication with the Polar Prince, an hour and 45 minutes into the two-hour descent to the wreckage on 18 June.

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The vessel was reported missing eight hours after communication was lost.

The rescue mission ended five days later when pieces of debris were found about 487m from the Titanic wreckage.