Sonar picked up banging sounds on Tuesday from underneath the water in the North Atlantic Ocean while searching for a submersible with five people onboard that went missing two days earlier on a dive to the Titanic wreckage, according to an internal US government memo on the search.

Crews detected banging sounds every 30 minutes – and four hours later, after additional sonar devices were deployed, banging was still heard, according to the memo. It was unclear when on Tuesday the banging was heard or for how long, based on the memo obtained by CNN.

“Additional acoustic feedback was heard and will assist in vectoring surface assets and also indicating continued hope of survivors,” a later update reads.

A Canadian P3 aircraft also located a white rectangular object in the water, according to that update, but another ship set to investigate was diverted to help research the acoustic feedback instead, according to that update.

Rolling Stone was first to report the news Tuesday night.

The US Coast Guard said underwater noises were detected by a Canadian P-3 aircraft, prompting the relocation of resources to explore their origin. But “searches have yielded negative results,” the agency tweeted.

“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,” the US Coast Guard added.

OceanGate told CNN they have no information to share on this when reached for comment. CNN has also reached out to Canadian authorities for comment.

The report comes amid a multinational race against time to find the submersible and its five passengers before their oxygen runs out.

As the massive search stretched into its third day, more ships and aircraft have joined the mission.

A spokesperson for the US Navy said the military branch is sending subject matter experts and a “Flyaway Deep Ocean Salvage System” to help in the rescue mission for the commercial submersible, which disappeared Sunday morning and as of Tuesday night, had just over 30 hours of oxygen left.

The system has the capacity to lift and recover large, bulky and heavy undersea objects, like the small submersible.

The equipment and personnel were expected to arrive at St. John’s, Newfoundland, by Tuesday night, the spokesperson said.

Now just let ALL of that sink in.

And apparently a lot of supposedly “smart” people thought this entire venture was a great idea!?! 😳

But first let me just say – I do hope that rescuers are able to find the mini-sub and save the passengers.