(This story was updated to add new information.)

The former scientific director of the ill-fated Titan submersible and a Mexican diver whose lifelong dream was realized during a previous trip to the Titanic will testify Thursday when hearings resume into the implosion that captivated the world for four days before the Titan's tragic fate was revealed.

The Titanic-visiting vehicle imploded 2 miles below sea level on June 18, 2023. Its wreckage was found on the ocean floor about 330 yards off the bow of the Titanic. All five people on board were killed: OceanGate Expeditions founder Stockton Rush, who was piloting the 22-foot submersible, a British billionaire, a French explorer and a Pakistani-born businessman and his son.

On Monday, the Coast Guard began two weeks of public hearings in North Charleston, South Carolina, aimed at finding out what went wrong.

Titan sub's haunting last message:'All good here'

Developments:

◾ The Coast Guard revealed at the hearing one of the final, haunting messages from the crew: "All good here."

◾ In a statement this week Jane Shvets, counsel for OceanGate, expressed "deepest condolences to the families and loved ones of those who died" and hopes that the hearing "will help shed light on the cause of the tragedy."

◾ No testimony was scheduled for Wednesday. The hearings reconvene Thursday and are being broadcast live on the U.S. Coast Guard channel.

Former OceanGate employee had no faith in Titan

Steven Ross, OceanGate's former scientific director, will be the next in a series of former employees testifying at the hearing. Among those to testify so far was David Lochridge, OceanGate’s former operations director, who claimed his concerns about the safety of Titan were ignored by officials with the Occupational Safety and Health Administration. Lochridge testified he finally dropped the complaint after 10 months when it had drawn no OSHA investigation. 

OceanGate’s former engineering director, Tony Nissen, testified Rush pushed hard on costs and schedules and was difficult to work with. Nissen described post-dive hull crack problems that he observed in the Titan serial 1 hull, a novel carbon fiber design, in 2018 and 2019. Nissen claimed he was fired in 2019 for voicing safety concerns.

In an emailed statement to USA TODAY, OceanGate said Nissen's testimony pertained to a prototype hull that was never used on Titanic expeditions and was not used after 2019.  After Nissen left the company in 2019, the company said it manufactured a new carbon fiber hull which was the one used on the Titanic expeditions.

In later testimony, Tym Catterson, a former OceanGate contractor, said he believes it wasn't the carbon fiber, but the glue that failed − "cyclic fatigue of the glue, every time they do a dive the hull would collapse a little in the center. Not a lot, not enough that you would see it with your eye."

Rush had declined to seek certification for Titan with any international maritime groups, saying its innovative design was “outside of an already accepted system.” He also said OceanGate could not innovate and make quick changes if it had to deal with the multiyear approval cycles.

Catastrophic Titan sub disaster:A year later the search for answers continues.

Lifelong ambition realized for Renata Rojas

Bonnie Carl, OceanGate’s former human resources and finance director, told the hearing panel that Lochridge had advised a potential customer, Renata Rojas, that Titan was not safe before her 2022 trip. The Mexican diver, who is scheduled to testify Thursday, had dreamed of visiting the Titanic wreck as a child. She has said it took her 30 years to save up the $250,000 ticket, but her dream was realized aboard Titan in 2022.

"I'm not a millionaire," she told the BBC then. "I made a lot of sacrifices in my life to be able to get to Titanic. I don't have a car, I didn't get married yet, I don't have children. And all those decisions were because I wanted to go to Titanic."

She said she wept when the Titanic came into view. She was amazed at how close to the wreckage the sub got: "Amazing to realize that you're at the Titanic. It's no longer a myth for me. It's reality, it's right there."

What happened to the company that owned Titan?

Two weeks after the incident, OceanGate said on its website it had suspended "all exploration and commercial operations." Its headquarters in Everett, Washington, was shuttered. Founded in 2008, its business license expired on June 7, according to Washington Department of Revenue records. The nonprofit research wing of the company, called OceanGate Foundation, was launched in 2010 but also closed in 2023, according to Washington Department of Revenue records.

OceanGate Inc. also operated a subsidiary, OceanGate Expeditions, out of the same office. According to Washington records, it closed on March 31, 2021.

OceanGate is being represented at the hearing by Jane Shvets and Adrianna Finger of Debevoise & Plimpton LLP.

What happened to the Titan?

The Titan's trip, expected to take eight hours, began at 8 a.m. on June 18, 2023, about 435 miles off the coast of Newfoundland, Canada. An hour and 45 minutes later, the submersible's support ship lost contact with the Titan. At 3 p.m., the Titan failed to surface, and the frantic search and rescue operation that ensued transfixed the world for four days.

On board were Stockton Rush, CEO of OceanGate Inc., the company that built the vessel; Paul-Henri Nargeolet, 73, a French deep-sea explorer; Hamish Harding, 58, a British pilot and adventurer; Shahzada Dawood, 48, a Pakistani-British businessman and his 19-year-old son, Suleman Dawood.

It was not until 11:48 a.m. on June 22 that the U.S. Coast Guard announced the discovery of a debris field. The vessel likely suffered a "catastrophic implosion" and OceanGate announced all occupants of the Titan had been lost.

Who is investigating the Titan implosion?

The Transportation Safety Board of Canada and the French Marine Casualty Investigation Authority are working with the U.S. Coast Guard and the National Transportation Safety Board to conduct "parallel safety investigations" on the incident.

French authorities are involved because one of the dead was Titanic expert Nargeolet, a French citizen. Canadian authorities are involved because the Titan submersible was transported to the dive site aboard the Canadian-flagged support vessel Polar Prince, which launched from Newfoundland.

The U.S. Coast Guard hearings that began Monday are looking into what was known about the safety and strength of the Titan vessel.

The Titanic also brought tragedy

The Titanic captured the nation's imagination in 1912, the largest and most well-appointed cruise ship of its time. But the ship hit an iceberg on April 15 of that year and quickly sank, killing more than 1,500. About 700 passengers were rescued. The wreck was discovered on Sept. 1, 1985, about 400 miles from the coast of Newfoundland.

Hundreds of books have been written about the ship. James Cameron's film "Titanic" was released in 1997 and is among the highest-grossing films of all time.