(NewsNation) — A group of House lawmakers are demanding information about a UAP crash retrieval program that a whistleblower claims is being covered up by the Pentagon.

The six lawmakers, led by Rep. Tim Burchett, asked the intelligence community inspector general in a letter to provide any and all information about the alleged crash retrieval program by mid-September.

The whistleblower, David Grusch, said in an open congressional hearing last month that he’s provided information about the crash retrieval program to the inspector general. Grusch told members of a House Oversight subcommittee during that hearing he could not provide names of people with first-hand knowledge of the crash retrieval in a public setting.

Lawmakers investigating the alleged crash retrieval program have said they have been denied access to a secure facility that would allow them to review classified information.

Burchett and others are pushing House Speaker Kevin McCarthy to establish a select committee on UAPs, which would them subpoena power and access to secure facility to view classified information, Burchett told The Hill at an event last week.

“We’re running into a lot of roadblocks there, and that’s the problem with this whole thing. It just creates more and more conspiracy theories because our federal government is so arrogant and so bloated, and they’ll just run out the clock,” Burchett said at the event. “I’m guilty of this as well, but Americans want their pizzas in 30 minutes or less, and that’s about our dadgum attention span.”

The hearing last month featured three witnesses who have first-hand knowledge of UAP sightings. Grusch, a former intelligence officer, claimed the government has recovered “non-human biological pilots” from downed UAPs, which the Pentagon has denied.

In the hearing, Grusch said he couldn’t speak on much of his knowledge because it is classified. But the investigating members told The Hill they are being slowed by the Pentagon on getting a classified hearing with Grusch started.

“The excuse that the Department of Defense is using for us not being able to get a SCIF is that Grusch doesn’t have an active [security] clearance. So unless he has active clearance, they’re saying that he can’t divulge that information to us, which, one, I believe is false,” Rep. Anna Paulina Luna said at The Hill event. “The Department of Defense is literally trying to stonewall us.”

The Hill contributed to this report.