Rescue efforts to find the missing Titanic submersible are entering their decisive hours . The vessel, named Titan, lost communication with tour operators on Sunday, June 18, while about 435 miles south of St John's in Newfoundland, during a voyage to the Titanic shipwreck off the coast of Canada.
On board the Titanic sub is the British billionaire adventurer Hamish Harding as well as UK-based businessman Shahzada Dawood, his son Suleman Dawood, and OceanGate's chief executive and founder Stockton Rush, reportedly with French submersible pilot Paul-Henri Nargeolet.
Rescuers are searching an area 2.5-miles below the surface of the sea. The temperatures are freezing cold and it is too deep for light to penetrate. In these pitch black conditions, it is easy to hit the ocean floor suddenly as subs have only a limited field of vision from their lights.
According to PA, as of Wednesday afternoon it was believed that just 20 hours of oxygen remained in the vessel, which meant it would run out at some point on Thursday morning. The 6.7m (22ft)-long OceanGate Expeditions vessel, which has British billionaire adventurer Hamish Harding on board, reportedly had a 96-hour oxygen supply in case of emergencies.
Read more: The Welsh adventurer who visited Titanic shipwreck in submarine
The BBC has reported that the US Coast Guard has estimated oxygen could run out for those on board at 07:18am eastern time in the US, which is 12:18pm here in the UK. Ten extra ships and several remote submarines are said to be joining the search on Thursday, which will more than double operations.
Rescue officials have said that they have to remain "optimistic and hopeful" about the search, but the captain leading the search has also said: "We don't know where they are, to be frank with you". The search site has expanded because of sounds detected on Tuesday and Wednesday.
The search now covers an area twice the size of US state Connecticut, and a sub-surface area 2.5 miles (4km) deep. But it's not clear whether the noises came from the submersible. Former US Navy submarine commander, David Marquet, told the BBC the noises may not be coming from the submersible.
"I don't think the noise is them, it could just be natural sounds," he said. "We're hearing noises and more ships are coming into the area, and then we're hearing more noises, and I don't think that's a coincidence."
The Polar Prince, which is the research vessel the Titan was launched from, will remain the command centre for the search, the BBC says. It sits not far from the Titanic wreck site. In the meantime, camera-equipped remote-controlled vehicles (ROVs) will be scanning the depths of the seafloor through out the day.
