Listen to This Article Enhance your reading experience by listening to this article.

A “debris field” was discovered on Thursday by a robotic deep-sea vessel searching for a missing tourist submersible on the ocean floor near the wreck of the Titanic, the US Coast Guard said.

Experts are reviewing the information gathered by the remotely operated vehicle that was deployed from a Canadian ship, the agency said on Twitter, without offering additional details. A press conference to explain the findings was scheduled for 3pm ET (1900 GMT).

The desperate search for the 22-foot Titan submersible had reached a critical stage on Thursday morning, when the air supply for the five people on board was estimated to have nearly run out – or possibly run out.

The van-sized Titan, operated by OceanGate Expeditions, began what was to be a two-hour descent at 8am (1200 GMT) on Sunday but lost contact with its support ship.

The submersible set off with 96 hours of air, according to the company, which means the oxygen would likely have been exhausted by Thursday morning, assuming the Titan is still intact. Precisely when depends on factors such as whether the craft still has power and how calm those on board are, experts say.

Another robot from a French research ship also dove toward the seabed on Thursday to search for signs of the Titan submersible.

Even if located in time, a rescue operation would face enormous logistical challenges in retrieving the submersible from more than 2 miles below the surface.

Rescuers and relatives of the Titan’s five occupants took hope when the US Coast Guard said on Wednesday that Canadian search planes had recorded undersea noises using sonar buoys earlier that day and on Tuesday.

But remote-controlled underwater vehicles searching where the noises were detected did not yield results, and officials cautioned the sounds might not have originated from the Titan. US Coast Guard rear admiral John Mauger told broadcaster NBC earlier on Thursday that the search would continue throughout the day.