(NewsNation) — A Missouri senator was “surprised” to learn how many unidentified aerial phenomena the U.S. government has come across, as lawmakers call for investigations into a whistleblower’s claims of a secret UFO program.

“The number of these is apparently huge, huge. And that is something that the government has, the best I can say about it, downplayed, if not kept from the public, for a long, long time,” said Missouri Sen. Josh Hawley.

Hawley says while he can’t assess the truth of Grusch’s allegations, he says the government has admitted there are many UAP sightings that are “unaccounted for.”

“I don’t have any basis to evaluate them but do some of the details that he’s alleging, do they sound plausible? Yeah, sure. They sound plausible, based on what I’ve seen this government do in other instances,” Hawley said.

This was in reference to the government’s response to the Chinese spy balloon spotted over the U.S. back in January.

“What we learned from the Chinese spy balloon incident is that one part of the government actively concealed it from other parts of the government,” Hawley explained. “Because that’s what they do all the time.”

A House oversight committee has vowed to hold open hearings to address the whistleblower’s allegations.

David Grusch, an Air Force veteran and former member of the National Geospatial Intelligence Agency alleged the U.S. government has recovered non-human craft for decades. He recently filed a whistle-blower complaint, stating he gave what he referred to as classified “proof” to Congress and the Intelligence Community Inspector General.

Hawley says though he can’t verify Grusch’s claims, they track with what he has heard in briefings.

“He’s saying that the government knows more about this than they have previously let on. That doesn’t really surprise me. Because it looks to me like the government has been tracking these UAPs for a long time now, and has not been saying much about it,” said Hawley.

However, not all lawmakers are convinced.

“If we’d really found this stuff, there’s no way you could keep it from coming out … My gut belief is if there’s a physical piece of a spacecraft or an intact spaceship, we would’ve known about it by now,” said South Carolina Sen. Lindsey Graham.

Hawley doesn’t buy that argument, saying the government is good at keeping secrets when it wants something to stay hidden.

Unidentified aerial phenomena (UAP), formerly UFOs, in theory could include alien spacecrafts, but the two aren’t synonymous.

The Defense Department’s All-Domain Anomaly Resolution Office considers a UAP “anything in space, in the air, on land, in the sea or under the sea that can’t be identified and might pose a threat to U.S. military installations or operations.”

In a statement to NewsNation, the Pentagon said, to date, “AARO has not discovered any verifiable information to substantiate claims that any programs regarding the possession or reverse engineering of extraterrestrial materials have existed in the past or exist currently.”

However, Grusch is claiming very few people are aware of the alleged secret UAP program, saying even those at the Pentagon who respond to UAP reports are in the dark.

“I have plenty of senior, former, intelligence officers that came to me, many of which I knew almost my whole career, that confided in me that they were part of a program,” Grusch claimed. “They provided me documents and other proof, that there was in fact a program that the UAP Task Force was not read into.”