A Royal Canadian Navy ship HMCS Glace Bay has been on scene since about 8 a.m. ET Thursday morning. The ship provides a medical team specializing in dive medicine and a six-person mobile hyperbaric recompression chamber, according to officials.

Canadian Coast Guard ships John Cabot, Ann Harvey and Terry Fox are on scene and ready to provide rescue equipment and personnel should assistance be required. A Royal Canadian Air Force CP-140 Aurora aircraft is also maintaining continuous on-scene support with additional aircrews and assets, according to officials.

-ABC News' Luke Barr

The U.S. Coast Guard announced via Twitter late Thursday morning that "a debris field was discovered within the search area by" a remotely operated vehicle (ROV) "near the Titanic" wreckage.

"Experts within the unified command are evaluating the information," the U.S. Coast Guard tweeted.

The Coast Guard is set to hold a briefing on the findings from the Horizon Arctic's ROV at 3 p.m. ET.

Despite their onboard oxygen tank expected to be depleted sometime Thursday morning, one doctor says they may have more time if the passengers are still alive. He estimates the five people aboard the lost Titanic tourist sub could survive for 10 to 20 hours with air still circulating through the experimental capsule.

Dr. Richard Moon, a professor of anesthesiology at Duke University, said that despite conditions being dire, those aboard the OceanGate Expedition's submersible could extend the oxygen available after its tank is depleted by staying calm and moving as little as possible.

"The actual amount of time that they have is unpredictable, but it's probably less than 24 hours after the final oxygen in the tank is depleted," Moon, director of the Duke Center for Hyperbaric Medicine and Environmental Physiology, told ABC News.

Read more here.

-ABC News' Bill Hutchinson

The U.S. Coast Guard announced via Twitter on Thursday morning that a remotely operated vehicle (ROV) deployed by the French vessel L'Atalante has entered the water in the search area.

The U.S. Coast Guard also gave an update on the conditions at sea, saying winds were at 14 mph with gusts up to 19 mph, swells were 4 to 5 feet and the air temperature was 50 degrees Fahrenheit.

The United States Coast Guard commander leading the search for a missing submersible off the coast of Newfoundland, Canada, said Tuesday morning that crews in multiple aircraft have flown over an area of the Atlantic Ocean "roughly about the size of Connecticut" while "looking for any signs of surfacing."

"As we continue on with the search, we're expanding our capabilities to be able to search under the water as well," Rear Adm. John Mauger, commander of the First Coast Guard District, told ABC News' Robin Roberts during an interview on "Good Morning America."

A commercial vessel with remotely operated vehicles is now on scene that will allow rescuers to search underwater, according to Mauger.

"This is a complex case," he added. "The Coast Guard doesn't have all the resources to be able to affect this kind of rescue, although this is an area that's within our search zone."

In many cases, Mauger said, the Coast Guard's role is to coordinate all of the assets and technical expertise that can be used in a search, in addition to operating aircraft or ships when necessary.

"In this particular case, we've established a unified command with the United States Navy, with the Canadian Armed Forces, with the Canadian Coast Guard and with the private operator OceanGate Expeditions to make sure that we understand what's needed and deploy all available equipment to the scene that could be used to locate this submersible, whether it's on the surface or down beneath the surface," he said.

Crews have been working "around the clock" to locate the deep-sea vessel since it lost contact with its operator on Sunday morning, according to Mauger.

In the last 24 hours, a Canadian aircraft has been dropping sonar buoys into the water that can pick up sound the submersible may be emitting. Vessels that have the capability to listen with their own sonar equipment are also on scene, according to Mauger.

"If they are making sound, that's certainly one of the ways that we're going to use to locate them," he said.