Controversial Fox News host Tucker Carlson has been known to embrace eccentric conspiracy theories. On his own program in June of this year, Carlson went on a tirade against the metric system, calling it “tyranny.” But in last week’s episode of the History Channel program Ancient Aliens, Carlson appeared to support an even farther-out theory.

In an interview with British journalist Nick Pope that aired on the November 22 edition of Ancient Aliens, Carlson claimed that a “knowledgeable” source has told him that the United States government possesses physical evidence that alien spacecraft have landed on Earth — or at least, crash-landed.

“I’ve heard this from someone who I think is knowledgeable on the subject that there is physical evidence that the U.S. government is holding, um, that, you know, would tell us a lot more – about what these objects are,” Carlson told Pope on the program, as seen in the video excerpt below on this page.

Pope then asked Carlson if he was referring to UFO “wreckage.”

“That is correct,” Tucker told the Ancient Aliens interviewer.

Of course, Carlson’s openness to the existence of UFOs and aliens on Earth is not new. In July, Carlson interviewed Donald Trump for a Fox News segment, raising the subject with him.

Trump told Carlson at the time that he did not consider himself a “believer” in UFOs, and said, “personally, I tend to doubt” that aliens have visited Earth in spaceships. But Trump left the door open, adding, “you know, I guess anything is possible.”

Carlson also asked Trump if he believed the claim that the government was holding UFO wreckage in an Air Force facility. But Trump replied, “I don’t assume it’s correct.”

Nonetheless, Trump told Carlson that he had “an open mind” on the subject.

At the time of Carlson’s interview, the U.S. Defense Department had recently briefed Trump on a series of sightings by Navy pilots of objects in the sky that they could not identify. The objects appeared to be moving at “hypersonic speeds,” according to the Fox News report on Carlson’s interview with Trump.

In 2007, the Central Intelligence Agency issued a report documenting the intelligence agency’s own investigations of the UFO phenomenon. The 84-page report, which remains available to read online via CIA.gov, notes that at least two U.S. presidents — Ronald Reagan and Jimmy Carter — claimed that they had experienced UFO sightings.

The study acknowledged “documents” that claimed to prove “the recovery of UFO wreckage” from an alleged Roswell, New Mexico, crash site. But the CIA report said that, “most if not all of these documents have proved to be fabrications.”