Search teams are racing against time to find a submersible that went missing during a dive to the Titanic’s wreck.
Five people were on board when contact with the small tourist sub was lost about an hour and 45 minutes into its dive on Sunday.
The rescue operation has expanded into deeper waters in the mid-Atlantic, but so far there has been no sign of it.
The five on board include British businessman Hamish Harding, and father and son Shahzada and Suleman Dawood.
As of Monday afternoon, the US coast guard said the five crew members had roughly four days of oxygen left.
A commercial pipe-laying ship, Deep Energy, with remote submersibles has arrived at the site, a deep-sea search and recovery expert has told the BBC.
Oceanographer David Mearns, who knows Mr Harding through an explorer’s club, said he was hopeful the vessel’s subs could reach the 3,800m (12,500ft) depth of the Titanic wreck to search for the missing vehicle.
Businessman Mr Harding, 58 – a renowned explorer who has flown to space and holds three Guinness World Records – is aboard, and said at the weekend he was “proud to finally announce” he was part of the mission.
The US Coast Guard said research ships the Polar Prince – which is used to transport submersibles to the wreckage site and was the support ship on Sunday’s tourist expedition – and Deep Energy were continuing to search the ocean’s surface.
A Canadian P3 Aurora aircraft is carrying out sonar searches of the areas, the Coast Guard confirmed, adding that the total area searched as of Tuesday morning was more than 10,000 sq miles (26,900 sq km).
On Tuesday, France’s sea ministry diverted the Atalante, a vessel equipped with a subsea robot, to assist with the search.