OceanGate Inc. gave a statement Thursday, saying those aboard the Titan vessel "have sadly been lost" ... calling them "true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world's oceans."

Officials say they located a debris field about 1,600 feet from the bow of the Titanic wreckage. Within that debris field, there was 5 "major" pieces of debris discovered to lead them to believe the vessel imploded.

The announcement comes just hours after a debris field was spotted near the Titanic's wreckage Thursday, and experts quickly got to work on evaluating what they found ... while a friend of 2 of the missing men claimed it was a landing frame and rear cover of the vessel.

The 22-foot-long sub, dubbed Titan, was first reported missing Sunday evening by its parent company, OceanGate Expeditions. The org says it first lost communication with its deep-sea voyagers about a couple hours into their descent ... and flagged the authorities hours later when it failed to emerge to the surface when it was scheduled to.

Since then, the U.S. Coast Guard and even Canadian officials have engaged in a full-blown search and rescue effort -- deploying all sorts of teams and equipment in hopes of finding Titan ... not to mention its five occupants, including OceanGate CEO Stockton Rush -- who's said to have been piloting the submersible on this particular mission.

OceanGate offers tourism rides down to the Titanic for $250k a pop. The other people who were inside included British explorer Hamish Harding, researcher/diver Paul-Henri Nargeolet and Pakistani businessman Shahzada Dawood, as well as his son Suleman.

The sub is reported to have limited life support ... including only 96 hours worth of breathable air which would have run out Thursday morning.

Search crews detected banging noises over their sonars during the hunt on Tuesday in the Atlantic Ocean, going off in 30-minute intervals ... and according to CNN, an internal U.S. government memo says the noise would help assist the crew in finding the vessel.

OceanGates' technology for its submersible has also come under scrutiny in recent days. While parts of Titan were made with top technology, other elements -- including several components on the inside -- were revealed to have been comprised of makeshift consumer goods ... including gaming remote controls, basic light fixtures, and other simple parts.

Reports have indicated that a former employee of OceanGate once tried flagging what he claimed were safety concerns about Titan to his bosses in 2018 -- only to be allegedly fired after doing so ... at least according to a whistleblower complaint detailing his allegations.

Experts have said the likelihood of the passengers' survival was slim to none, considering the circumstances.

Even former Coast Guard Captain Andrew Norris filled us in on the multiple miracles that would be needed in order to ensure the passengers survived the terrifying incident.

We covered all in the latest episode of The TMZ Podcast, available on all podcast platforms.