Five people, including the company CEO, were aboard the sub when it imploded.
All passengers are believed to be lost after a desperate dayslong search for a submersible carrying five people that vanished while on a tour of the Titanic wreckage off the coast of Newfoundland, Canada.
The 21-foot deep-sea vessel, operated by OceanGate Expeditions, lost contact about an hour and 45 minutes after submerging on Sunday morning with a 96-hour oxygen supply. That amount of breathable air was forecast to run out on Thursday morning, according to the United States Coast Guard, which was coordinating the multinational search and rescue efforts.
The U.S. Coast Guard will be the organization leading the investigation into the OceanGate sub incident.
The NTSB announced the news on Friday via Twitter, noting it will "contribute to their efforts."
A Las Vegas father and son told ABC News OceanGate CEO Stockton Rush pressured them for months into taking two seats on the now failed mission to the Titanic, making bold claims about the vessel's safety.
Financier Jay Bloom shared text messages between himself and Rush where Rush dismissed concerns from Bloom and his son Sean about taking the trip on the Titan submersible.
"While there's obviously a risk it's way safer than flying in a helicopter or even scuba diving," Rush texted.
"He sort of had this predisposition that it was safe," Bloom told ABC News. "And anybody who disagreed with him, he felt it was just a differing opinion."
Bloom added that Rush flew out to Las Vegas in a homebuilt plane to convince him to attend the voyage aboard the submersible.
"He flew it all the way to Vegas. And I was like, 'This guy is definitely down to take risk,'" Bloom said.
-ABC News' Sam Sweeney
The U.S. National Transportation Safety Board will be participating in the multiagency investigation into the Titan sub incident, an NTSB spokesperson told ABC News.
The U.S. agency joins the U.S. Coast Guard and the Transportation Safety Board of Canada (TSB), which deployed its members to St. John’s, Newfoundland and Labrador.
The TSB says it will conduct a "safety investigation regarding the circumstances of this operation conducted by the Canadian-flagged vessel Polar Prince."
-ABC News' Amanda Maile
White House press secretary Karine Jean-Pierre said the administration's "hearts go out to the families and the loved ones of those who lost their lives" on the Titan submersible.
"They have been through a tragic ordeal over the past few days and we are keeping them in our thoughts and prayers," she said.
She also thanked all parties who participated in search and rescue efforts this week.
"We would also like to thank the United States Coast Guard, our Canadian, British and French partners, and everyone who participated in the search and rescue efforts these past couple of days," Jean-Pierre said. "This whole effort has been a testament to the skill and also the professionalism that the men and women who serve our nation continue to demonstrate, continue to show each and every day."
-ABC News' Justin Gomez
