Vessel passengers may face dwindling oxygen levels and cold

Missing sub has "about 40 hours of breathable air left," Coast Guard says

Coast Guard officials estimate there is "about 40 hours of breathable air left" in the missing submersible that went missing on its way to view wreckage from the Titanic.

The vessel lost contact 1 hour and 45 minutes into its dive Sunday, the US Coast Guard said. At that time, officials estimated it had 96 hours of life support.

"We know there's about 40 hours of breathable air left based on that initial report," Capt. Jamie Frederick, with the First Coast Guard District, said at a Tuesday news conference.

Five people are on board the missing sub.

Coast Guard: Titanic tour sub search efforts "have not yielded any results"

From CNN's Kristina Sgueglia

So far, the Coast Guard and its partners' "search efforts have not yielded any results" in the hunt for the missing Titanic tour submersible, Capt. Jamie Frederick, with the First Coast Guard District Response Department, said Tuesday.

Frederick said the Coast Guard has been coordinating with other agencies since Sunday, including the US Navy and Canadian Coast Guard, to conduct the search.

On Tuesday, the vessel Deep Energy, a 194-meter pipe-laying vessel with underwater capabilities, arrived on scene and rendezvoused with the Polar Prince, the vessel the submersible launched from to commence a dive at the last known position of the sub and at the approximate position of the Titanic wreck, Capt. Frederick said at a news conference.

He said other vessels are currently en route to join the effort, including some privately owned vessels that are "making preparations" to help with the "very complex" search.

The Canadian vessel John Cabot is expected to arrive this evening, along with other Canadian Coast Guard vessels.

The US Navy’s supervisor salvage and diving command is working with US Transportation Command to bring additional assets, he said.

Vessels will be staged at St. John's in Canada, Frederick said.

Coast Guard is working around the clock to conduct complex search for missing submersible

The US Coast Guard is working "around the clock" to try to find the missing submersible with five people on board, an official said Tuesday.

The submersible was reported missing on Sunday after it lost contact and didn't return to the surface at its expected time.

Capt. Jamie Frederick, with the First Coast Guard District, said it has been a "complex search" that requires specialized equipment.

The Coast Guard doesn’t have all of the expertise and equipment that they need, which is why they are calling on other agencies and countries for help, Frederick said, including the United States Navy and the Canadian Armed Forces.

"The unified command brings that expertise and additional capability together to maximize effort in solving this very complex problem," he said at a news briefing Tuesday.