Five people were killed June 18, 2023, in the Titan submersible that was journeying to see the wreckage of the Titanic, touching off a wave of scrutiny about the safety practices of OceanGate, the company that operated the voyage, and an eye on the private undersea exploration industry more generally. A hearing in South Carolina on Monday by the U.S. Coast Guard revealed new details about the implosion of the Titan sub, including the final text sent from people in the sub to operators on the surface of the Atlantic Ocean.

The first person to testify Monday was Tony Nissen, OceanGate’s former engineering director, who said he was under tremendous pressure to get the sub working, according to CBS News, but stressed that he didn’t believe testing had been rushed. However, Nissen noted that it was a “difficult question to answer” simply because “given infinite time and infinite budget, you could do infinite testing,” according to the Associated Press.

Nissen also testified the Titan sub was struck by lightning during a test in the Bahamas in 2018, something that may have potentially compromised the hull. As the New York Times notes, the company experienced 70 equipment issues in 2021 and 48 in 2022, according to testimony on Monday. And Nissen said he was fired in 2019 because he wouldn’t approve an expedition that year over his concerns for the integrity of the sub.

The former finance director of OceanGate, Bonnie Carl, who testified that she had “major concerns,” with the equipment at the company. Carl said she left the company after it received criticism for lax safety standards, including from film director James Cameron, who builds and uses his own submersibles. Stockton Rush, the founder of OceanGate, was one of the five people killed during the implosion last year, and the majority of the public criticism has been directed at him.

Investigators said the Titan was stored outside in harsh, cold conditions the winter before the implosion, which may have contributed to the tragedy. The Coast Guard is conducting an investigation under the Marine Board of Investigation and the hearings that started Monday are expected to last about two weeks, according to the Associated Press.

“There are no words to ease the loss endured by the families impacted by this tragic incident,” Jason Neubauer from the Coast Guard Office of Investigations said during the hearing, according to CBS News. “But we hope that this hearing will help shed light on the cause of the tragedy and prevent anything like this from happening again.”