A robot is combing the sea floor for debris from the fatal implosion of the Titan submersible as authorities in both the US and Canada turn their attention from search and rescue to investigating what led up to the maritime disaster and whether any laws were broken.
The US Coast Guard has convened a Marine Board of Investigation to probe the implosion -- the "highest level of investigation the Coast Guard conducts," US Coast Guard chief investigator Capt. Jason Neubauer announced Sunday.
The board will work to determine the cause of the catastrophic implosion and fatalities, as well as make recommendations "to pursue civil or criminal sanctions as necessary," Neubauer said.
For now, investigators are prioritizing recovering debris from the sea floor. Military experts found debris from the ill-fated submersible about 1,600 feet from the bow of the Titanic on Thursday, the US Coast Guard previously said.
"My primary goal is to prevent a similar occurrence by making the necessary recommendations to enhance the safety of the maritime domain worldwide," Neubauer said Sunday.
The salvage operation comes as questions remain about the submersible's design, the materials used in its construction, what caused it to implode and when exactly the implosion happened.
The Titan was 1 hour and 45 minutes into its descent to the Titanic's wreckage on the ocean floor last Sunday when it lost contact with its mother ship, kick-starting a dayslong multinational search and rescue operation in the North Atlantic that ended Thursday, with the discovery of its debris.
The US Coast Guard's investigation is one of several currently underway. Authorities in Canada also tasked with probing the incident will be reviewing voice recordings from the submersible's mother ship, the Polar Prince, Canadian officials said.
Canadian investigators boarded the Polar Prince on Saturday "to collect information from the vessel's voyage data recorder and other vessel systems that contain useful information," Kathy Fox, chair of the Transportation Safety Board of Canada, said Saturday. A voyage data recorder stores audio from the ship's bridge.
Meanwhile, the Royal Canadian Mounted Police is looking into whether "criminal, federal, or provincial laws may possibly have been broken."
"There's no suspicion of criminal activity per se, but the RCMP is taking initial steps to assess whether or not we will go down that road," RCMP Superintendent Kent Osmond said at a Saturday press briefing.
US and Canadian authorities have also been conducting interviews in the port of St. John's, Canada, where the Polar Prince returned Saturday with its flags at half-mast.
"This case has been extremely complex, involving a coordinated international, interagency and private sector response in an unforgiving and difficult to access region of the ocean," Mauger said Sunday.
The Coast Guard announced the vessel suffered a "catastrophic implosion," killing everyone on board.
Those killed were OceanGate Expeditions CEO Stockton Rush; British businessman Hamish Harding; French diver Paul-Henri Nargeolet; and Pakistani-born businessman Shahzada Dawood and his son, Suleman, who were British citizens.
What's happening on the ocean floor?
The same remotely operated vehicle that found the submersible's debris field last week is now involved in the operation to recover debris from the Atlantic Ocean, according to a statement from Pelagic Research Services, first seen by CNN, on Sunday.
The Odysseus 6K, a remotely operated vehicle, was on the seafloor in its fourth dive since arriving at the Titan rescue site on Sunday, according to a statement from Pelagic Research Services, first seen by CNN, on Sunday.
The company added Odysseus' heavy lift capabilities "have been utilized and continue to be utilized" in the Titan recovery mission but would not confirm if debris had been recovered and referred CNN to the US Coast Guard, which is leading the investigation into the implosion and recovery effort.
Capt. Neubauer declined to give details on the recovery operation Sunday, but said that "resources are on site and capable of recovering the debris."
Five different major pieces of debris from the submersible were found Thursday morning, officials said. Each end of the pressure hull was found in a different place, according to Paul Hankins, US Navy director of Salvage Operations and Ocean Engineering.
Remotely operated vehicle missions are expected to continue for about another week, according to Jeff Mahoney, spokesperson for Pelagic Research Services.
Any attempts to recover anything from the debris field will warrant a larger operation in tandem with Deep Energy, another company helping with the mission, because the debris will likely be too heavy for Pelagic's ROV to lift by itself, Mahoney told CNN on Friday.
Pieces of the submersible will be examined as investigators seek to understand why it imploded.
The US Navy said it detected an acoustic signature consistent with an implosion on Sunday in the general area where the submersible was diving when it lost communication, a senior Navy official told CNN.
The sound was determined to be "not definitive," the official said, and the multinational efforts to find the submersible continued as a search and rescue operation before the debris field was found.
Vessel used materials that 'simply didn't work,' expert says
While the debris field is mapped out and pieces from the submersible are collected, experts are raising questions about the Titan's design.
A CNN review of OceanGate's marketing material, public statements made by Rush and court records show that even as the company touted a commitment to safety measures, it rejected industry standards that would have imposed greater scrutiny on its operations and vessels.
A former employee who worked briefly for the company as an operations technician had concerns about the hull's thickness and adhesion, he said, speaking to CNN on the condition of anonymity.
"This was a company that was already defying much of what we already know about submersible design," Rachel Lance, a Duke University biomedical engineer who has studied physiological requirements of survival underwater, said on CNN Thursday. She noted some of the vessel's design materials "were already large red flags to people who have worked in this field."
She said the unconventional combinations of materials used in the Titan, including carbon fiber, posed safety risks because "over the course of repeated pressurizations, they tend to weaken."
"This is not exactly what, in my opinion, would be innovation because this is already a thing that has been tried and it simply didn't work," she said.
When submersible expert Karl Stanley was aboard the Titan for an underseas excursion off the coast of the Bahamas in April 2019, he felt there was something wrong with the vessel when loud noises were heard and sent an email to Rush, the CEO of OceanGate Expeditions, sounding the alarm on suspected defects.
"What we heard, in my opinion ... sounded like a flaw/defect in one area being acted on by the tremendous pressures and being crushed/damaged," Stanley wrote in the email, a copy of which has been obtained by CNN.
When asked for comment about Stanley's email, a spokesman for OceanGate told CNN they were unable to provide any additional information at this time.
OceanGate co-founder Guillermo Sohnlein urged people not to rush judgment over the implosion. "There are teams on site that are still going to be collecting data for the next few days, weeks, maybe months, and it's going to be a long time before we know exactly what happened down there," Sohnlein told CNN on Friday. "So I would encourage us to hold off on speculation until we have more data to go on."