London, 21 June 2023 (dpa/MIA) - Underwater noises detected in the search area of a missing deep-sea vessel is a “target” and a “focus” for the rescue operation, the US Coast Guard has said.

The submersible, named Titan, lost communication with tour operators on Sunday while about 700 kilometres south of St John’s, Newfoundland, during a voyage to the Titanic shipwreck off the coast of Canada.

The US Coast Guard announced earlier on Wednesday that the Canadian P-3 aircraft detected underwater noises.

Later on Wednesday, the US Coast Guard tweeted: “Three vessels arrived on-scene Wednesday morning, the John Cabot has side scanning sonar capabilities and is conducting search patterns alongside the Skandi Vinland and the Atlantic Merlin.”

Rear Admiral John Mauger told CBS News: “This is an incredibly complex site there, you have to remember that it’s the wreck site of the Titanic, so there is a lot of metal and different objects in the water around the site.

“That’s why it’s so important that we’ve engaged experts from the navy that understand the science behind noise and can classify or give us better information about what the source of that noise may be.

“In the meantime, it’s something, it’s a target, it’s a focus for us to look at.

“We’ve deployed the remote-operated vehicles and the surface vessel, the Canadian Coast Guard surface vessel, that has sonar capability in the vicinity of that to see if we can detect anything in the water in that area.”

The Titan has five people on board, including British billionaire adventurer Hamish Harding, and the 6.7m (22ft) long OceanGate Expeditions vessel may have less than 24 hours of oxygen left.

The others on board are Shahzada Dawood, his son Suleman and OceanGate’s chief executive and founder Stockton Rush, reportedly together with French submersible pilot Paul-Henri Nargeolet.

An array of vessels are involved in the search effort, including Bahamian research vessel Deep Energy, French research vessel L’Atalante, His Majesty’s Canadian Ship Glace Bay – for a mobile decompression chamber and medical personnel – and four Canadian Coast Guard vessels, according to the US Coast Guard.

Speaking to PA news agency, former Royal Navy submarine captain Ryan Ramsey said the rescue operation is made harder due to there being no replica of the Titan submersible to model a rescue attempt off should they find it.

He said: “It would have to be bespoke equipment. I don’t think anyone has planned for this kind of operation so they would have to create some kind of bespoke process to get a cable round or a fixing point on that particular submersible.

“The problem with that is, with most submersibles, they make two of them, they make two of them for reasons – for example, something does happen to one of them the rescuing porters can go see the other one and figure how they’re going to exercise the rescue.

“In this particular case, they only made one and so there’s no opportunity for people to work out what that solution is and to work that problem through and achieve a successful outcome.”

He added that Titan may never be found as search rescues continue their efforts in a race against time.

He said: “Hope is a very human emotion, and we should all hope that there is a successful outcome, I would really like to be proven completely wrong and they turn up on the surface, in the next few hours, they’re located, and everything ends well.

“But I think you have to be realistic, and the odds are against them in every single way possible.

“We may never know the outcome of this because they never detect it and so we have to make the assumption that this is not going to end as well as we would like.

“My thoughts go out to the families because they must be struggling through this time trying to comprehend what’s happening and hoping this is going to come to a successful conclusion but, hour by hour, as the time frame collapses, that’s very unlikely.”

The Explorers’ Club, of which Mr Harding is a founding member, shared an upbeat message on Wednesday morning.

President Richard Garriot de Cayeux said in a statement: “There is cause for hope, that based on data from the field, we understand that likely signs of life have been detected at the site.

In a statement on their website, deep water specialists Magellan said they were contacted by OceanGate on Monday and “immediately” offered knowledge of the site and expertise in operating at depth.

The company added that it has been working with UK and US agencies to move its specialist equipment and support crew to St John’s, Newfoundland, following instructions to mobilise from OceanGate.

The Ministry of Defence (MoD) said the UK-based Nato Submarine Rescue System (NSRS) team is available to offer expertise and guidance to the search operation.

But reports indicate the the depths involved in the search “greatly exceed” that which the NSRS can safely operate.

An MoD spokesperson said: “As the host nation for NATO’s multinational submarine rescue capability, we continue to monitor the incident in the North Atlantic and will guide and assist in any response activity as appropriate.”

Meanwhile, US media outlet Rolling Stone reported an internal US government memo said “banging” was detected by Canadian search aircraft in 30-minute intervals on Wednesday.

A former employee of OceanGate had raised concerns over “safety and quality control issues regarding the Titan to OceanGate executive management”, according to court filings.

David Lochridge, OceanGate’s former director of marine operations, claimed in the August 2018 court document he was wrongfully fired after flagging worries about the company’s alleged “refusal to conduct critical, non-destructive testing of the experimental design”.

After “issues of quality control” with Titan were raised, the filings say Mr Rush asked Mr Lochridge to conduct a “quality inspection” report on the vessel.

During this process, Mr Lochridge “identified numerous issues that posed serious safety concerns” but he was allegedly “met with hostility and denial of access” to necessary documents before later being fired.

The document claims he became concerned about a “lack of non-destructive testing performed on the hull of the Titan”, and that he “stressed the potential danger to passengers of the Titan as the submersible reached extreme depths”.

In a November 2022 episode of his Unsung Science podcast, CBS journalist David Pogue interviewed Mr Rush ahead of going on a Titan expedition to the wreckage.

In the podcast, Mr Rush told him: “You know, at some point, safety is just pure waste.

“I mean, if you just want to be safe, don’t get out of bed, don’t get in your car, don’t do anything.

Mr Pogue said that he had signed a waiver before going on the dive which allegedly said: “The experimental submersible vessel has not been approved or certified by any regulatory body” and that the trip could result in death.

OceanGate has been approached for comment.

On Tuesday, Captain Jamie Frederick of the US Coast Guard said a “unified command” of multiple agencies was formed on Monday to tackle the “very complex problem” of finding the submersible and estimated the Titan had “40 hours of breathable air” left.

It is now estimated there is around 20 hours of breathable air left on the submersible based on Capt. Frederick’s announcement.