- By Kathryn Armstrong
- BBC News
Rescuers searching for a tourist submarine near the Titanic wreck in the North Atlantic on Sunday heard a “noise” in the area near where the ship went missing.
According to the US Coast Guard, a Canadian P-3 aircraft heard the sound, which US Navy experts are investigating.
Underwater operations have been relocated to investigate the source.
But so far remote-controlled vehicles [ROV] The Coast Guard said it had “returned negative results.”
“Additionally, data from the P-3 flight has been shared with our US Navy experts for further analysis, which will be considered in future search plans,” the Coast Guard tweeted early Wednesday, adding that ROV searches were continuing.
According to an internal US government memo seen by US media, “bangs” were heard about 30 minutes apart on Tuesday.
Four hours later additional sonar was deployed and the sound could still be heard.
The BBC has contacted the Department of Homeland Security for comment.
On Sunday, five people were on board when the ship headed for the wreck, about an hour and 45 minutes into the sinking, or more than halfway through.
Search officials estimate the sub has less than 30 hours of oxygen left, meaning supplies will run out by about 10:00 GMT (06:00 EDT) on Thursday.
The five people on board were British businessman Hamish Harding, 58, British-Pakistani businessman Shahjata Dawood, 48, and his son Suleiman, 18, French explorer Paul-Henri Narcolet, 77, and Stockton Rush, 61, chief executive of Oceangate.
The team was sealed inside the sub using external bolts, meaning they couldn’t escape it even if it reappeared.
Chris Brown, an investigator and friend of Mr Harding’s, said the reported thunder sounds had “written all over them” and were “just what I expected Hamish to be”.
“If you keep making noise, it won’t pick up, but doing it every 30 minutes is instructive to humans,” he told BBC Breakfast.
“I’m sure they’re all conserving oxygen and energy because it’s cold and dark out there.”
After the sounds were detected, two members of the scientific community called the Explorers Club on board shared the exciting news.
“There is reason for optimism, based on data from the field, we understand that signs of life have been detected at the site,” the organization’s head said in a statement.
A search operation in the Canadian province of Newfoundland has so far turned up nothing. However, it is expanding to include more resources and recovery expertise from private companies.
The mission is complicated – there’s no communication from tour company OceanGate’s Titan companion, and visibility is quickly lost below the water’s surface because light can’t penetrate very far.
Bad weather remained in the area, although the US Coast Guard said these had improved on Tuesday.
With an area of 7,600 square miles (1,970 sq km), it is larger than the US state of Connecticut.
“Our crews are working around the clock to make sure we’re doing everything possible to find Titan and the five crew members,” Coast Guard Capt. Jamie Frederick said earlier.
US and Canadian agencies, navies and commercial deep-sea companies are all assisting in the rescue operation, which is being operated from the US city of Boston, Massachusetts. It used military aircraft, submarines and sonar buoys.
Captain Frederick said a major effort was underway to get heavy equipment to the search site.
Two Canadian Coast Guard vessels and a Royal Canadian Navy vessel equipped with a six-person mobile hyperbaric recompression chamber are also en route.
If equipped with a sub, this chamber can be used to treat or prevent decompression sickness, which occurs when divers are exposed to a rapid decrease in pressure.
Several private vessels are also assisting in the search, while France has returned a ship with a subsea robot and an ROV with a camera on board is investigating the last known location of the sub.
The commercial pipeline-laying vessel Deep Energy is assisting the research vessel Polar Prince, which was a companion vessel on Sunday’s cruise, to search the ocean’s surface.
During her maiden voyage from Southampton to New York in 1912, the Titanic hit an iceberg. More than 1,500 of the 2,200 passengers and crew on board died.
Its ruins have been extensively explored since their discovery in 1985.
OceanGate Expeditions charges guests $250,000 (£195,270) for its eight-day cruise to see the famous wreck, which sits 12,500ft (3,800m) on the bottom of the Atlantic Ocean.