The coast guard wasn't called until eight hours after the Titanic submersible went missing along with five crew members.
The Titan vessel was reported missing Sunday early evening about 435 miles (700 m) south of St. John’s, Newfoundland.
With just 96 hours of oxygen reserves on board, a desperate serach has been launched involving multiple Coast Guard agencies and a number of private vessels.
But the official search wasn't launched until 5.40pm ET when the Polar Prince, the boat the submersible launched from, contacted United States Coast Guard.
According to a spokesperson for the USCG the original call came in to the First District Command Cente eight hours after it went missing.
The sub started the trip at 8am ET and was expected to resurface at 3pm but contact was lost an hour and 45 minutes after it dived.
Mirror Online has contacted OceanGate for comment.
The expedition was led by OceanGate, making its third voyage to the Titanic, which struck an iceberg and sank in 1912, killing all but about 700 of the roughly 2,200 passengers and crew.
The US Coastguard confirmed that there are five people on board the missing submarine. OceanGate Expeditions, the private company which organises deep-sea expeditions, has confirmed in a statement that it owns the missing submersible.
The statement said: "We are exploring and mobilising all options to bring the crew back safely. Our entire focus is on the crewmembers in the submersible and their families."
Speaking at a press conference, Captain Jamie Frederick of the US Coast Guard First District said that the original 96 hours of oxygen supply was an estimate from data they have on the OceanGate Expeditions submersible.
"From the data we were using, the starting point was 96 hours, we're now at approximately 40 to 41 hours left."
This means that the five crew on board have enough oxygen to last them until 11am BST on Thursday, June 22.
The eight-day expedition to the site of the famous wreck costs around $250,000 (£195,270) per person. The trip on OceanGate Expeditions' carbon-fibre submersible is described as a "chance to step outside of everyday life and discover something truly extraordinary."
The submersible can seat five people, according to the company, including a pilot, three paying guests and a "content expert." The dive to the wreck, including descent and ascent, takes around eight hours in total.
The wreckage of the Titanic now lies in two parts, with the bow and stern separated by around 800m, and a huge field of debris around the vessel.
The crew on board the missing submersible had made no contact with the support crew for more than eight hours. Usually, signals would be sent to the mother ship every 15 minutes.
