(NewsNation) — The U.S. Coast Guard is stressing the search for a missing submersible remains a search-and-rescue mission despite concerns over dwindling oxygen supplies for the five passengers on board.

In a news conference Wednesday afternoon, the Coast Guard said they have exponentially expanded the search area. The surface search now covers an area two times the size of Connecticut, and the underwater search area extends two and a half miles deep.

U.S. Coast Guard Capt. James Frederick said the search is now focused on an area where Canadian aircraft detected underwater noises. The noises are being analyzed by a team of Navy experts to determine if they are biological or man-made.

Frederick stressed that the mission is still very much a search-and-rescue operation, and there is still hope the submersible and passengers could be recovered. He noted there are limited food and water rations on board in the event of an emergency and stressed that the amount of oxygen on board is just one measure used to calculate how long those inside can survive.

“There comes a point when you have to make a tough decision, but we’re not there yet,” Frederick said, when asked if there was a point the operation would shift to recovery mode.

Horizon Maritime, which supports OceanGate Expeditions, held a news conference Wednesday afternoon as they mobilized the Horizon Arctic to aid in the search.

“OceanGate runs an extremely safe operation,” Horizon Maritime President Sean Leet said. “Our priority right now is getting that submersible located and bringing those people back safely.”

Also at the news conference was Miawpukek First Nations Chief Joe Misel, who expressed concern for the passengers and their families and said he is praying for their safe return.

“We ask everyone around Canada and the world to pray with us,” Misel said.

On Tuesday, a Canadian aircraft searching for the missing Titan submersible detected “underwater noises” from the vicinity of the location the crew was touring the wreck site of the Titanic ocean liner.

The crew searching for the sub heard noises every 30 minutes and again four hours later after additional sonar devices were deployed, The Independent reported. The Coast Guard declined to confirm the 30-minute interval report but reiterated the noises are being analyzed and used to inform the search.

The Coast Guard said Wednesday that they’re continuing to search and work closely with Navy experts for further analysis. They also clarified that they have not made any statements regarding underwater “banging or tapping,” contrary to some reports.

“I want to reiterate this is a very complex search and the unified team is working around the clock to bring all available expertise and assets to bear as quickly as possible in an effort to solve this very complex problem,” Frederick said.

The primary search area is vast, 900 miles east off the coast of Cape Cod, 400 miles south of Newfoundland, Canada, where the crew launched its research expedition last Friday.

U.S. and Canadian military planes and boats are working together in the search. An underwater robot has also started searching in the area of the Titanic wreckage.

“We will do everything in our power to effect a rescue,” Frederick said.

The U.S. Navy is sending its “flyaway deep ocean salvage system” in case the submersible is found and needs a lift out of the water. The Coast Guard said the equipment was scheduled to arrive in St. John’s on Wednesday night.

Three vessels arrived Wednesday: Canadian Coast Guard boat John Cabot, which has sonar capabilities, as well as commercial vessels Skandi Vinland and the Atlantic Merlin.

Even more were en route as of Wednesday night, the Coast Guard said in a news release. They include:

• Canadian CGS Ann Harvey 
• Canadian CGS Terry Fox 
• Motor Vessel Horizon Arctic (remote-operated vehicle) 
• French Research Vessel L’Atalante (remote-operated vehicle) 
• His Majesty’s Canadian Ship Glace Bay (mobile decompression chamber and medical personnel) 
• Air National Guard C-130  
• Remote-operated vehicle from Magellan, the company that mapped the Titanic wreck

However, locating and recovering the Titan, if possible for rescue crews, will pose a complex and time-consuming mission due to the great depth of water involved.

Tuesday night, three C-17 aircraft from the U.S. Air Force arrived from Buffalo, New York, to St. John’s carrying “rescue-related cargo.”

As of Tuesday, search crews had covered more than 10,000 square miles.

Among the passengers of the submersible, called the Titan, is Hamish Harding, a 58-year-old British businessman. Harding lives in Dubai in the United Arab Emirates, according to Action Aviation, a company for which Harding serves as chairman.

The CEO and founder of OceanGate Expeditions, Stockton Rush, is also among the passengers, along with Pakistani businessman Shahzada Dawood and his son Suleman. The fifth person is believed to be Paul-Henry Nargelot, the submersible’s pilot.

Meanwhile, more details continue to come to light about safety warnings made directly to OceanGate leading up to the Titan going missing. There were concerns raised about dangers when the vessel reached extreme depths dating back to 2018.