Secret Navy sensors detected a possible implosion around the time the Titan’s communications failed.

The U.S. Navy, using data from a secret network of underwater sensors designed to track hostile submarines, detected “an anomaly consistent with an implosion or explosion” in the vicinity of the Titan submersible at the time communications with the vessel were lost on Sunday, two senior Navy officials said on Thursday.

But with no other indications of a catastrophe, one of the officials said, the search was continued.

Both officials, who spoke on condition of anonymity to discuss operational details, said that the analysis of undersea acoustic data and information about the location of the noise had been shared with the Coast Guard official in charge of the search.

But without visual or other conclusive evidence of a catastrophic failure, one of the officials said, it would have been “irresponsible” to immediately assume the five passengers were dead, and the search was ordered to continue even though the outlook appeared grim.

The Navy’s acoustic analysis from the secret sensor network was first reported by The Wall Street Journal.

It was not clear how widely the Navy’s acoustical analysis was disseminated among the search team, or why the Navy had not made it public earlier.