The submersible that went missing during an expedition to view the wreckage of the Titanic is nearing a critical 96-hour mark at which it is expected to soon run out of oxygen for passengers to breathe.
The Titan submersible launched on Sunday in the north Atlantic Ocean with about four days of breathable oxygen but lost communications and failed to resurface at its scheduled time. Authorities have conducted a widespread search for the sub that has not yielded any results.
Experts have said the estimated amount of oxygen that the five passengers have to breathe is imprecise and could be extended if they have taken actions to conserve it.
Those searching for the passengers appeared to potentially have some reason for hope after detecting "underwater noises in the search area," but they could not conclude that the noises came from the submersible.
The search area for the sub has expanded to an area twice the size of Connecticut and in waters 2.5 miles deep.
Even if it is located soon, rescuers would still need to reach it with the proper equipment and then bring it to the surface before the oxygen runs out. The wreck of the Titanic is about 370 miles off the coast of Newfoundland, Canada and more than 2 miles below the ocean's surface, where sunlight cannot reach.
Jamie Frederick, a captain for the First Coast Guard District, maintained on Wednesday that the mission was still "100 percent" a search and rescue operation.
The First Coast Guard District tweeted early Thursday morning that the French vessel L'Atalante deployed a remotely operated vehicle and that a vehicle from the Canadian vessel Horizon Arctic reached the sea floor and began its search.
The passengers on the submersible include a British adventurer, a father and son who are Pakistani and a French explorer and Titanic expert. Its pilot is the founder of the company that operates the missing submersible.
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