SEARCHERS looking for the Titan vessel have admitted that they don't know the source of underwater banging noises that were heard - as less than 24 hours remain to save five crew trapped onboard.
US Coast Guard officials are holding onto hope of finding the missing submarine, working around the clock searching the vast 15,000 square mile area 900 miles east of Cape Cod, .
In a press conference on Wednesday afternoon, officials confirmed the Horizon Arctic is en route to aid in the search.
The powerful ship is a well-equipped vessel with underwater capabilities. It will likely arrive Thursday morning.
The ship would have arrived sooner but had to return to Newfoundland to retrieve deep-sea diving equipment, according to authorities.
"We are very aware of the time sensitivity around this mission," officials said.
"We're incredibly grateful for the full spectrum of international assistance that has been provided."
Rescue crews have dispatched two remote-operated vehicles (ROVs) to search the ocean surface and depths in the area of the Titanic wreckage, where they believe the Titan vessel may be.
On Tuesday evening, a Canadian P-3 aircraft heard banging noises in 30-minute intervals while looking for the vessel, which disappeared on Sunday during an underwater trip to see the Titanic wreck site 12,500 feet below.
Coast Guard Captain Jamie Federick confirmed the noises were once again heard by several aircrafts on Wednesday morning.
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"When you're in the middle of a search and rescue case, you always have hope. That's why we're doing what we do," Federick told reporters.
Despite the small glimmer of hope that the five crew members onboard the Titan may still be alive, Federick said officials have been unable to confirm the origin of the noises.
"With respect to the noises, specifically, we don't know what they are, to be frank with you," the Coast Guard captain said.
"We're searching in the area where the noises were detected."
Search crews said the two ROVs are "actively searching" an area two times the size of the state of .
Additional ROVs are en route to join the search operation in the North Atlantic, including the French ship Atalante, which is carrying the only underwater vehicle thought to be capable of winching the vessel to safety.
However, the boat is not expected to reach the area on Wednesday evening - just 12 hours before the crew’s oxygen supply is due to run out at midday on Thursday.
On board the ship is Victor 6000, a robot able to dive 20,000 feet underwater.
The unnamed robot can dive deeper than other equipment at the search site.
It also has arms that can be remotely controlled to cut cables or perform other maneuvers to release a stuck vessel, the operator said.
TITAN VESSEL GOES MISSING
Communication was lost with the $250,000-a-head voyage just an hour and 45 minutes into its 12,500-foot descent to the ruins of the Titanic on Sunday.
The Titan sub was due to resurface that afternoon but failed to do so, sparking a frantic rescue mission.
The final message sent from the vessel placed it directly above the Titanic - which lies at a depth of 12,500 feet around 373 miles off the coast of Newfoundland, Canada.
The vessel descended into the ocean depths with only 96 hours of breathable oxygen.
On board the missing sub is crew members British billionaire Hamish Harding, British-based tycoon Shahzada Dawood and his 19-year-old son Suleman, French diving expert Paul-Henry Nargeolet, and OceanGate submarine boss Stockton Rush.
Those on board are faced with grueling conditions due to the "improvised" and "experimental" nature of the vessel.
Strange footage from inside the submarine reveals that it is all unusually run by an Xbox-style controller and can mainly be operated using only one button.
"It should be like an elevator, it shouldn't take a lot of skill," explained Rush in an interview with .
The sub-operators themselves declared it was an "experimental" sub that "had not been approved by any regulatory body."
Journalist David Pogue traveled onboard the Titan last year and shared his concerns over some components of the sub that seemed "off-the-shelf, sort of improvised."
He told the "You steer this sub with an Xbox game controller [and] some of the ballast is [built from] abandoned construction pipes."
And the inside lighting was bought from a camping shop.
He also explained that there is "no way" to communicate with the mini-van size vessel, nor can anyone inside the sub escape without external help.
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Passengers are sealed within the main cabin by hefty bolts secured from the outside and have to be removed using an external crew.
"There's no backup, there's no escape pod," he said. "It's get to the surface or die."