The five people on board the missing submersible close to the wreck of the Titanic have "about 40 hours of breathable air" left, the US Coastguard has said.

In an update on Tuesday, Captain Jamie Frederick said the search for the vessel, called Titan, had not yielded any results so far.

An ROV (remotely operated underwater vehicle) has been deployed at the site and has a camera on board.

A unified command has been set up, consisting of "expertise from the United States Coast Guard, the United States Navy, Canadian Armed Forces and Coast Guard, and the Titan's parent company, Ocean Gate Expeditions", Mr Frederick said.

Since Sunday, combined search efforts have covered an area of 7,600 square miles, he added.

A Canadian P-3 aircraft is conducting a six hour search and several C-130 aircraft and another P-3 are scheduled to fly on Tuesday afternoon and evening, he said.

The combination of a surface search and a subsurface search make it an "incredibly complex operation", Mr Frederick said.

A retired US Navy submarine commander said the hunt for the Titan is like "searching a football pitch with a magnifying glass

Captain David Marquet told Sky News he finds it "concerning that they haven't found it yet"

He went on: "It's probably on the bottom - it's not on the surface. I imagine they're going inch-by-inch and searching a big area on the bottom where it could be.

"We could get lucky and we could find it, but we don't like to bank on luck."

Captain Marquet said the tone of the Tuesday briefing suggested "they've kind of admitted the chances are really, really slim"

The Coast Guard and other search and rescue crews have swarmed a remote area in the Atlantic in search of the vessel, which went missing on Sunday with five people on board.

Rescuers have expanded their search into deeper waters.

It is understood from the vessel's operator, OceanGate Expeditions, that the Titan had a 96-hour oxygen supply in case of emergencies.

The five people on board are British billionaire Hamish Harding, Pakistani businessman Shahzada Dawood and his son Suleman, chief executive and founder of OceanGate Expeditions, Stockton Rush, and French submersible pilot Paul-Henri Nargeolet.

Mr Dawood is married and has two children, the family said in a statement. He is vice chairman of Pakistan's Engro Corporation.

He and his son Suleman, who is currently studying at university, are British citizens.

The major search and rescue operation is taking place some 435 miles south of Newfoundland, Canada.

The Canadian research icebreaker Polar Prince, which was supporting the Titan, reportedly lost contact with the vessel about an hour and 45 minutes after it submerged.

The wreckage of the Titanic, which sank in 1912 after hitting an iceberg, lies at a depth of about 12,500 feet (3,810 metres).

The Titan submersible usually takes two hours to descend to the wreck

Cashlanderr:
Their life is at stake, lord pls help