The U.S. Navy holds unseen videos of unidentified flying objects (UFOs) — or unidentified aerial phenomena (UAP), as the Department of Defense (DOD) prefers to call them — but will not release the footage publicly because it would "harm national security," a Navy spokesperson wrote Wednesday (Sept. 7).

The admission came in response to a Freedom of Information Act (FOIA) request filed by the government transparency site The Black Vault, which has previously shared thousands of pages of UFO-related documents received via FOIA requests to the CIA and other government agencies. The Black Vault filed the FOIA request to the U.S. Navy in April 2020 — just one day after the Navy declassified three now-infamous videos shot by Navy pilots showing high-tech aircraft moving in seemingly impossible ways. The Black Vault requested that the Navy now turn over any and all other videos related to UAP.

More than two years later, the government responded with a letter that both confirmed that more UAP videos exist and denied the request to turn them over due to national security concerns.

"The release of this information will harm national security as it may provide adversaries valuable information regarding Department of Defense/Navy operations, vulnerabilities, and/or capabilities," Gregory Cason, deputy director of the Navy's FOIA office, wrote in a response letter. "No portions of the videos can be segregated for release."

Cason added that the Navy was able to declassify the three UAP videos released in April 2020 only because the videos had been previously leaked to the media and had already been "discussed extensively in the public domain." The Navy deemed it possible to officially release the footage "without further damage to national security," Cason wrote.

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Interestingly, in its response to The Black Vault's request, the Navy did not make any attempts to conceal the existence of additional UAP videos. There are clearly more videos of inexplicable UFO encounters in the Navy's archives, but how many and what they depict will have to remain a mystery for now.

It's clear, however, that the U.S. military takes the potential threat of UAP very seriously. In May 2022, the DOD held its first public hearing on UFOs since the 1960s. The hearing primarily discussed a June 2021 Pentagon report that revealed U.S. Navy pilots had reported 144 UAP sightings since 2004. More recently, the DOD announced that it will receive federal funding to open a new office focused exclusively on managing reports of UFO sightings by the U.S. Army, Navy and Air Force.

Originally published on Live Science.