Missing Titan sub: 'We don't know what the noises are, quite frankly'
Search and rescue efforts to locate the missing submersible are continuing in a race against time, as ITV News' Lucy Watson, Neil Connery and Martin Stew report
Rescuers searching for a submersible in the Atlantic Ocean have said they "don't know" whether noises picked up by sonar technology from underneath the water are coming from the missing vessel.
Five people - including three British nationals - remain missing after contact was lost with their OceanGate Expeditions submersible last Sunday.
The vessel, named Titan, had been due to complete a voyage to the Titanic shipwreck.
A French unmanned robot called Victor 6000 is due to join the search for the submersible, which experts believe has only hours left of oxygen supply left.
Operated by a 25-strong crew, the robot, which has remotely controlled arms capable of cutting cables and other manoeuvres to release the vessel will head towards the Titanic wreck, some 12,500ft below.
The family of a British billionaire aboard the missing sub have claimed the rescue operation was raised far 'too late.'
Speaking to the Telegraph, Kathleen Cosnett, the cousin of missing Hamish Harding, said that it took 'far too long' for tour provider OceanGate to raise the alarm.
The 69-year-old told the newspaper: "It's very frightening. [It] took so long for them to get going to rescue [them], it’s far too long. I would have thought three hours would be the bare minimum.
“My thoughts are with them all.”
'When you're in the middle of a search and rescue case you always have hope,' US Coast Guard Captain Jamie Frederick told reporters
On Tuesday, an internal US government memo revealed that "banging sounds" were detected by search and rescue teams.
But speaking to reporters on Wednesday, US Coast Guard Captain Jamie Frederick said he was "quite frankly" unable to say exactly where the noises originated from.
"We need to have hope, but I can't tell you what the noises are," he said.
He added: "The good news is we're searching in the area where the noises were detected and will continue to do so.
"And we hope that when we're able to get additional ROVs, which will be there in the morning, the intent will be to continue to search in those areas where the noises were detected.
"And if they're continuing to be detected then put additional ROVs down in the last known position where the search was originally taking place."
Captain Frederick gave an update on the size of the search zone, saying the surface search is now approximately two times larger than the size of the US state of Connecticut.
He added the sub-surface search is up to "two and a half miles deep", and reiterated the need to "factor in the ever changing weather conditions, currents and sea states that expand the search area every hour".
In a separate news conference, the chairman of Horizon Maritime Services - the company which owns the Polar Prince ship from which Titan was launched - described the situation as "unprecedented".
Captain Frederick said the search zone is being 'exponentially' expanded by changing weather and sea conditions
He insisted that OceanGate runs an "extremely safe operation" when pressed on whether all safety protocols were followed by the firm up to and during Titan's launch.
Rescuers searching for the submersible said it is estimated that there was only "40 hours of breathable air" left onboard on Tuesday - which is enough to last until Thursday morning, UK time.
Several estimates have been suggested of when exactly the amount of breathable air will run out.
The US Coast Guard has estimated "breathable air" could run out shortly after 10am BST (5am ET).
On Wednesday afternoon, US Coast Guard Rear Admiral John Mauger told the BBC there was estimated to be less than 20 hours off oxygen left aboard the Titan.
Asked why it is difficult to offer an accurate prediction, he said: "One of the factors that makes it hard to predict how much oxygen is left is that we do not know the rate of the consumption of oxygen per occupant on the sub."
Rear Admiral Auger added that the banging has given authorities "a target".
He 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."
Correspondent John Ray reports on the enormous difficulties facing the rescue operation
The US Coast Guard said underwater noises were detected by the Canadian aircraft, prompting the relocation of resources to explore their origin, but "searches have yielded negative results".
"Additionally, the data from the P-3 aircraft has been shared with our US Navy experts for further analysis which will be considered in future search plans," they added.
OceanGate told CNN they have no information to share on this when reached for comment.
As the massive search stretched into its third day, more ships and aircraft have joined the mission.
Hamish Harding, a 58-year-old British billionaire and chairman of Dubai-based firm Action Aviation, is one of the missing crew.
Correspondent Lucy Watson takes us through the geography of where the submersible is expected to be
A friend of Mr Harding described him as "the quintessential British explorer".
Colonel Terry Virts said: "Some people watch Netflix and some people play golf, and Hamish goes to the bottom of the ocean or into space or, you know, he sets world records flying around the planet... he loves adventure.
"I don't think Hamish is an adrenaline junkie at all, that's not Hamish.
"He likes exploration. And, you know, exploration involves risk, but he's also very methodical about it."
The submersible was carrying one pilot and four "mission specialists", including Mr Harding, when it lost contact with its mother ship about 1 hour and 45 minutes into its descent.
Chris Parry, a retired navy rear admiral from the UK, said without an "emitting signal" from the missing deep-sea vessel, it will be "impossible" to find in the timescale.
He told LBC: "I'm afraid the odds are vanishingly small.
"Obviously, we want to remain hopeful and optimistic but there are two problems here - one is actually finding the thing and secondly is how on earth are you going to get it off the seabed.
"It's never been done before and I don't think anybody's got any ideas about how to do it at the moment."
He added: "You've got this vastly complex seabed with all the debris of the Titanic, you've got hills and canyons and everything, and I'm afraid to say without an emitting signal from the vehicle itself it's almost, well, I'd say it's impossible to find in the timescale."
A spokesperson for the US Navy said the military branch is sending subject matter experts and a "Flyaway Deep Ocean Salvage System" to help in the rescue mission.
The system has the capacity to lift and recover large, bulky and heavy undersea objects, like the small submersible.
A Canadian pipe-laying vessel with underwater capabilities is among the fleet of assets joining the operation, alongside other vessels and aircraft.
The search zone covers an area about 900 miles east of Cape Cod, Massachusetts, and 13,000 feet deep.
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