(NewsNation) — Contradicting David Grusch’s claim is science writer and conspiracy theory debunker Mick West, who tells “Elizabeth Vargas Reports” that what Grusch is saying isn’t accurate and that “the video evidence doesn’t stack up.”

Grusch claims the government is covering up UFOs and that he has seen evidence of a secret crash retrieval program. The Air Force veteran alleges the U.S. has even retrieved bodies from other species. Grusch spoke about these claims exclusively to award-winning investigative journalist Ross Coulthart, reporting for NewsNation.

Blurry videos of unidentified flying objects have long been a staple of those looking for evidence that stories of UFOs may not be conspiracy theories. In recent years, the government has taken a more vocal role in investigating such sightings, with Congress forming an official U.S. government “Unidentified Aerial Phenomena” task force, recently renamed to the “All Domain Anomaly Resolution Office,” or AARO.

NewsNation has confirmed Grusch’s credentials and resume, but has not seen or verified the alleged proof he said he provided to investigators. Grusch said he can’t show NewsNation the evidence for national security reasons.

“I don’t think what he’s saying is accurate. I think it’s possible he’s believing what he’s saying, but it’s an incredible story that really needs some actual verification,” West said.

West said he does believe that UFOs “are a real thing” and that there may be some unidentified flying objects out there, but he doesn’t believe there are aliens.

NewsNation’s Brian Entin contributed to this report.