The Department of Defense has top-secret classified briefings and a classified video about a UFO incident.

The U.S. Navy acknowledged the existence of the information, which concerns a 2004 encounter between the USS Nimitz and strange unknown aerial objects, in response to a public records request from Vice.

Last year, the Navy for the first time acknowledged that three UFO videos -- one from the 2004 USS Nimitz incident and two from 2015 -- were real videos of unidentified flying objects.

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Top-secret UFO files could damage U.S. national security, the Navy says.

Top-secret UFO files could damage U.S. national security, the Navy says. (PhonlamaiPhoto/iStock)

Responding to Vice's Freedom of Information Act request, the Navy said it had "discovered certain briefing slides that are classified TOP SECRET. A review of these materials indicates that are currently and appropriate Marked and Classified TOP SECRET under Executive Order 13526 and the Originial Classification Authority has determined that release of these materials would cause exceptionally grave damage to the National Security of the United States."

“We have also determined that ONI possesses a video classified SECRET that ONI is not the Original Classification Authority for,” the letter continued.

Vice reports that a Pentagon spokesperson said the Navy has the video of the mysterious incident in its possesion but has no plans to release it.

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“However, I can tell you that the date of the 2004 USS Nimitz video is Nov. 14, 2004," the spokesperson told Vice. "I can also tell you that the length of the video that’s been circulating since 2007 is the same as the length of the source video. We do not expect to release this video.”

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