Five people, including the company CEO, were aboard the sub when it imploded.
All passengers are believed to be lost after a desperate dayslong search for a submersible carrying five people that vanished while on a tour of the Titanic wreckage off the coast of Newfoundland, Canada.
The 21-foot deep-sea vessel, operated by OceanGate Expeditions, lost contact about an hour and 45 minutes after submerging on Sunday morning with a 96-hour oxygen supply. That amount of breathable air was forecast to run out on Thursday morning, according to the United States Coast Guard, which was coordinating the multinational search and rescue efforts.
A source familiar confirmed to ABC News that there were reports of "banging" that were picked up by sonar in the search area on Tuesday morning, but nothing has yet been found.
The U.S. Coast Guard had said early Wednesday that an aircraft with sonar capability "detected underwater noises in the search area," but remotely operated vehicles were unable to find the origin of the sound.
-ABC News' Luke Barr
Magellan, an international exploration company that digitally mapped the Titanic wreckage last year, said Wednesday that it is "ready to support" the search for the missing submersible and is "fully mobilized to help."
The U.K.-based company told ABC News that it was contacted by the submersible’s operator, OceanGate Expeditions, early Monday and "immediately offered our knowledge of the specific site and also our expertise operating at depth considerably in advance of what is required for this incident."
"We have been working full-time with U.K. and U.S. agencies to secure the necessary air support to move our specialist equipment and support crew," Magellan said in a statement.
When asked for comment about media reports that U.S. authorities have failed to give Magellan the necessary permits to participate in the search, the company told ABC News it "does not not wish to comment on any specific media report."
-ABC News' Emma Ogao
The U.S. Coast Guard announced via Twitter early Wednesday that a Canadian aircraft with sonar capabilities had "detected underwater noises in the search area."
Remotely operated vehicle operations (ROV) were then relocated "in an attempt to explore the origin of the noises," according to the Coast Guard.
"Those ROV searches have yielded negative results but continue," the Coast Guard tweeted.
A former employee of OceanGate alleged in a 2018 counterclaim lawsuit that he was fired for raising concerns about quality control and testing of potential flaws in the same experimental submersible that went missing this week.
David Lochridge, an engineer and submarine pilot, claimed in his counterclaim against OceanGate that he was hired in 2015 by the Everett, Washington, company to ensure the safety of all crew and clients during the submersible and surface operations of the vessel called Titan. But when he expressed concerns about the design and testing of the minisub's hull, he said he was terminated by the company.
OceanGate had initially sued Lochridge alleging, among other things, breach of contract, fraud and misappropriation of trade secrets -- all claims he denied.
In its lawsuit, OceanGate accused Lochridge of breaching his contract by discussing the company's confidential information with the Occupational Health and Safety Administration "when he filed a false report claiming that he was discharged in retaliation for being a whistleblower."
-ABC News' Bill Hutchinson
