A "debris field" has been discovered by an underwater robot that is conducting a search for a missing submersible with five people on board near the wreck of the Titanic, media reports said Thursday.

The development came after rescuers insisted that the multinational mission to locate the craft was still focused on finding the crew alive despite fears that the vessel's oxygen may have run out.

"Experts within the unified command are evaluating the information," the US Coast Guard said in a tweet.

According to the  coast guard, the debris field was found "within the search area by an ROV (Remotely Operated Vehicle) near the Titanic."

Two more robots were deployed Thursday in the search for the Titan sub, lost somewhere in the North Atlantic between the ocean's surface and more than two miles (nearly four kilometers) below.

The 21-foot (6.5-meter) Titan began its descent at 8:00 am on Sunday and had been due to resurface seven hours later.

However, the craft lost communication with its mothership less than two hours into its trip to see the Titanic.

The Titanic's grave is situated 400 miles off the coast of Newfoundland in Canada, and more than two miles below the surface of the North Atlantic.