An astrophysicist who used to work for the Pentagon's secret UFO division has claimed the US military is in possession of "off-world vehicles not made on this Earth".
Eric W Davis, who's been subcontracted to and consulted for the Pentagon since 2007, told the New York Times last week investigations into some of the materials gathered led him to conclude "we couldn't make it ourselves".
Davis gave a briefing to the Defence Department in March about vehicles "not made on this Earth", the Times reports, following up classified briefings last year on similar unexplained material.
The Pentagon's UFO unit, formally known as the Unidentified Aerial Phenomenon Task Force, has been shrouded in mystery since its existence was first confirmed in 2017 when former punk singer Tom DeLonge - of Blink 182 fame - released clips supposedly showing Navy pilots chasing UFOs in 2004.
The US Navy confirmed the clips were real last year, and in April formally declassified them.
Harry Reid, formerly the Senate majority leader and currently involved in the Unidentified Aerial Phenomenon Task Force, said its main task was to figure out if another country here on Earth was "using breakout aviation technology that could threaten the United States".
Senator Marco Rubio, who ran for the Republican nomination to become President in 2016, said he was concerned another country had acquired "some technological leap" over the US.
"Maybe there is a completely, sort of, boring explanation for it. But we need to find out," he told the Times.
The Unidentified Aerial Phenomenon Task Force has been told to make "at least some of its findings" public, the Times reported.
Luis Elizondo, who used to direct the Pentagon's UFO investigations but now works for DeLonge's To The Stars Academy, said there would soon be a a "new transparency" around the Pentagon's UFO activities.
"It no longer has to hide in the shadows."
Members of the task force didn't respond to requests for comment.