The race to save the five passengers on the missing Titan submersible continues, growing more desperate as the hours tick by and the remaining oxygen on the sub falls to dangerously low levels.

The Titan sub, which lost communications with its operator on Sunday morning, now has under 20 hours worth of reserve oxygen. Five people are onboard the sub that was meant to take them to see the famous Titanic shipwreck.

On Tuesday, the Coast Guard announced that “underwater noises” had been detected underwater by Canadian aircraft helping in the rescue efforts. These noises were described as “banging” sounds and were coming from the vessel’s search area.

“Canadian P-3 aircraft detected underwater noises in the search area,” tweeted the US Coast Guard. “As a result, ROV operations were relocated in an attempt to explore the origin of the noises. Those TOV searches have yielded negative results but continue.”

USCG added that “the data from the P-3 aircraft has been shared with [their] U.S. Navy experts for further analysis which will be considered in future search plans.”

Additionally, the data from the P-3 aircraft has been shared with our U.S. Navy experts for further analysis which will be considered in future search plans. 2/2 #Titanic

— USCGNortheast (@USCGNortheast) June 21, 2023

According to internal emails sent to the Department of Homeland Security and obtained by Rolling Stone, these banging sounds could mean the crew is “alive and signaling.”

The emails say, “RCC Halifax launched a P8, Poseidon, which has underwater detection capabilities from the air.”

“The P8 deployed sonobuoys, which reported a contact in a position close to the distress position,” the email updates read. “The P8 heard banging sounds in the area every 30 minutes. Four hours later additional sonar was deployed and banging was still heard.”

So far, over 10,000 square miles have been searched but the vessel has still not been detected.

First Coast Guard District Response Coordinator Capt. Jamie Frederick reported that multiple agencies are coordinating their search and rescue efforts.

“While the Coast Guard has assumed the role of Search and Rescue Mission Coordinator, we do not have all of the necessary expertise and equipment required in a search of this nature,” said Frederick. “The Unified Command brings that expertise and additional capability together to maximize effort in solving this complex problem.”