The development came after organisers of the multinational response insisted the mission to locate the craft was still focused on saving the crew and passengers -- despite concerns that, even if the vessel is still intact, its oxygen may have run out.
The US Coast Guard has not confirmed whether the debris belonged to the small tourist sub, lost somewhere in a vast swathe of the North Atlantic between the ocean's surface and more than two miles (nearly four kilometers) below.
"Experts within the unified command are evaluating the information," the Coast Guard said in a tweet, adding that it would hold a press briefing at 3:00 pm (1900 GMT) in Boston.
But marine scientist and oceanographer David Mearns, who specialises in deep water search and recovery operations, said the development indicated a "catastrophic failure," probably "an implosion."
"They don't use phrases like 'debris field' unless there's no chance of a recovery of the men alive. A debris field implies a breakup of the submersible," he told Sky News.
"The only saving grace about that is that it would have been immediate, literally in milliseconds, and the men would have had no idea what was happening," added Mearns, who was friends with two of those onboard.
Based on the sub's capacity to hold up to 96 hours of emergency air, rescuers had estimated that the passengers, which include fee-paying tourists, may have run out of oxygen in the early hours of Thursday.
But as that possible deadline passed, US Coast Guard Rear Admiral John Mauger said rescuers were "fully committed" to search operations.
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