Titan Sub Missing: 'Debris field' discovered as search expands to ocean floor, says US Coast Guard

Here are the latest updates:

- 'Debris field' discovered as search expands to ocean floor

- The US Coast Guard said that an underwater vessel has located a debris field near the Titanic in the search for a missing submersible with five people aboard, a potential breakthrough in the around-the-clock effort.

- US Coast Guard says search to continue even as oxygen is feared to have exhausted

The US Coast Guard said the extensive search operation, which is underway over the past four days, will continue for the five persons onboard even as the supply of oxygen in the submersible is feared to have been exhausted. The rescue operation will continue as "people’s will to live really needs to be accounted for," Rear Adm. John Mauger said.

- How search teams could use sound to find the Titan sub -- and why it's a challenge

"It's not a simple problem," said Matt Dzieciuch, an ocean acoustics expert at the Scripps Institution of Oceanography. The ocean is a "noisy place," Dzieciuch said. There are many other potential sources of sound under water, including from fish, other animals and of course human-made instruments, he explained.

But it's still "speculative" whether the banging noises were a true signal of life, said Art Trembanis, a marine scientist at the University of Delaware. Even this kind of pattern could come from an underwater instrument making repeated noise.

- Authorities are hoping underwater sounds might help narrow their search, whose coverage area has been expanded to thousands of miles — twice the size of Connecticut and in waters 2 1/2 miles (4 kilometers) deep.

- Dr. Rob Larter, a marine geophysicist with the British Antarctic Survey, emphasized the difficulty of even finding something the size of the sub — which is about 22 feet (6.5 meters) long and 9 feet (nearly 3 meters) high. “You’re talking about totally dark environments," in which an object several dozen feet away can be missed, he said. "It’s just a needle in a haystack situation unless you’ve got a pretty precise location.”

- The area of the North Atlantic where the Titan vanished Sunday is also prone to fog and stormy conditions, making it an extremely challenging environment to conduct a search-and-rescue mission, said Donald Murphy, an oceanographer who served as chief scientist of the Coast Guard’s International Ice Patrol.

Experts say that the oxygen supply number is an imprecise estimate and could be extended if passengers have taken measures to conserve breathable air. And it’s not known if they survived since the sub disappeared.

Officials have expanded the coverage area to thousands of miles — twice the size of Connecticut and in waters 2 1/2 miles deep. Aeroplanes, ships, remote-operated underwater vehicles and a US Navy-owned specialized salvage system have been deployed, concentrating where unidentified noises had been heard for two days.

The banging noises, as detected by a Canadian plane with sonar capabilities on June 21, raised hopes of a possible discovery.

The submersible, which is capable of taking passengers to a depth of 4,000 metres, is run by OceanGate Expeditions founder. The five people onboard the sub include the company's CEO Stockton Rush, French Titanic expert Paul-Henri Nargeolet, British billionaire Hamish Harding and Pakistani businessman Shahzada Dawood and his 19-year-old son, Suleman.

With AP & Reuter inputs