The massive search operation that has been ongoing since Monday for the Titanic tourist submersible that went missing Sunday is believed to be without oxygen at this time.

Early Thursday morning, the US Coast Guard said that they have finally gotten a remote-operated vessel on the sea floor and has began searching for the missing submersible although the tank has likely run out of oxygen.

The five passengers that are on board are feared dead as oxygen levels are expected to last until today (Thursday morning).

Officials have reported that the submersible begins each trip with 96 hours of life support. The search has so far garnered widespread global attention and has seen rescue efforts from the Canadian and American Navy/Coast Guard and Air Force in attempts to locate the missing sub.

Emergency medical personnel and search vessels with extra capabilities headed to the scene early Thursday morning.

The Titanic wreckage is believed to be approximately 12,500ft below the sea and the submersible could possibly have vanished to those depths which is described as unusually impossible for any human to reach.

An update is expected soon.