The underwater robot, Victor 6,000, can reach up to 6,000 metres deep into the sea. Photo: Reuters

A French ship equipped with an unmanned robot able to search deep under water has arrived near the wreck of the Titanic to join a massive search for a missing submersible.

With just hours of oxygen believed to be left for the five people onboard the submersible Titan, the Atalante ship has begun operations at the scene in the North Atlantic, the French Research Institute for Exploitation of the Sea (IFREMER) said on Thursday.

The ship, which is operated by IFREMER, and its team were urgently dispatched from France on Tuesday.

It carries the Victor 6000, a remotely operated underwater vehicle (ROV) capable of descending to a depth of 6,000 metres.

Wealthy people on board

The Titanic wreck sits at a depth of 3,800 metres, making it a particularly difficult area to search – or reach for a potential rescue mission.

The Atalante has begun using its multibeam echo sounder to create a map of the nearby seabed to "allow Victor 6000 to have a more efficient dive," an IFREMER spokesperson said.

But the echo sounder, which bounces acoustic waves off the seafloor to work out its depth, would not be able to detect the submersible itself, the spokesperson added.

The tourist submersible Titan began its descent towards the wreck on Sunday, losing contact with its support ship on the surface two hours later.

It was carrying British billionaire Hamish Harding, Pakistani tycoon Shahzada Dawood and his son Suleman, the CEO of the company OceanGate Expeditions Stockton Rush, and French submarine operator Paul-Henri Nargeolet.

Based on the sub's capacity to hold up to 96 hours of emergency air, rescuers estimate that the passengers may run out of oxygen on Thursday.

AFP