A “debris field” has been found in the area where authorities are searching for the missing Titanic submersible four days after the vessel disappeared, the U.S. Coast Guard announced Thursday. In a race against the clock, the search and rescue mission, which started on Sunday, may be coming to a close amid the recent discovery—either for good or for ill. The Coast Guard said in a Tuesday press conference that the five passengers aboard had roughly 96 hours of oxygen with them, which could make Thursday the final day to find them alive.

“A debris field was discovered within the search area by an ROV near the Titanic,” the Coast Guard reported in a Twitter post. It continued, “Experts within the unified command are evaluating information.” The Coast Guard will be holding a press briefing at 3 p.m. EST.

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