A former intelligence community official testified Wednesday on an alleged covert government program to recover and reverse engineer crashed alien spacecraft.
David Grusch, a member of a previous Pentagon office tasked with investigating unidentified aerial phenomena, or UAPs, said he was informed of the alleged multi-decade program through his official duties, but was denied access to additional information.
The Pentagon said last month it hadn't found "any verifiable information to substantiate" the claims about crashed alien spacecraft.
MORE: Extraterrestrial 'technical surprise' is top concern, Pentagon UFO investigator says"My testimony is based on information I've been given by individuals with a long-standing track record of legitimacy and service to this country, many of whom have shared compelling evidence in the form of photography, official documentation and classified oral testimony to myself and many various colleagues," Grusch told lawmakers, stating he was driven to share it by a "commitment to truth and transparency."
"I am asking Congress to hold our government to this standard and thoroughly investigate these claims," he said. "But as I stand here under oath now I am speaking to the facts as I have been told them."
The remarks came during a bipartisan hearing held by the House Oversight Committee's national security subcommittee. The three witnesses included Grusch, David Fravor, a former commanding officer in the U.S. Navy, and Ryan Graves, executive director of Americans for Safe Aerospace.
Members of both parties stressed the need for greater clarity on UAPs. Many voiced concerns that unidentified aerial objects pose to national security.
"Today we are not just debating the existence of UAPs, we are deliberating on the principles that define our republic, which is a commitment to transparency and accountability," said Rep. Glenn Grothman, R-Wisc., who chaired the hearing.
Grusch asserted the U.S. government first became aware of non-human intelligence in the 1930s. When asked by Rep. Jared Moskowitz, D-Fla., if he has met people with direct knowledge of non-human-origin craft, Grusch said yes.
However, he told the committee he could not publicly disclose the names of those with firsthand knowledge and access to the alleged crash retrieval program, though he said that information was provided to the intelligence committees and the inspector general.
Grusch also said he couldn't publicly state when the supposed program began and who authorized it, stating much of that information is classified.
Lawmakers expressed a desire to talk with Grusch and other officials behind closed doors, such as in secured facility, to learn more.
When asked who the committee should call to testify in their next hearing, Grusch said he could provide a "cooperative and hostile list of individuals in the government who you should talk to."
Rep. Virginia Foxx, R-N.C., highlighted previous congressional testimony provided by Dr. Sean Kirkpatrick, who leads the Defense Department's All-Domain Anomaly Resolution Office tasked with examining UAPs, in which he said they did not find any evidence of extraterrestrial activity or off-world technology.
"This contradiction is a perfect example of why we need to inject transparency into our government," Foxx said.
Kirkpatrick recently told ABC News the vast majority of UAP sightings are readily explainable, with just 2% to 5% of reports containing unexplained anomalies. Also, he downplayed the existence of a secret program he may not be aware of.
"A number of these [whistleblowers] believe and have stated -- and we believe them now -- that they have seen something. And we are investigating," Kirkpatrick said.
Grusch was joined on Capitol Hill by two former Navy pilots: Fravor, who had a firsthand encounter with a UAP, and Graves, who created an organization aimed at increasing government transparency on UAPs.
Fravor described to the committee a 2004 episode where he and others spotted a small white object that looked like Tic Tac candy "moving very abruptly over the water like a ping pong ball." The encounter was captured in a 90-second video. Fravor said the incident was never investigated.
"What concerns me is there is no oversight from our elected officials on anything associated with our government processing or working on craft believed [to be] not from this world," Fravor said.
Rep. Matt Gaetz, R-Fla., made a guest appearance in the hearing to discuss a tip his office received about a UAP sighting at Eglin Air Force base, located in his congressional district in Okaloosa County. Gaetz said after a disagreement with military officials, he was allowed to see an image of four supposed UAPs in a diamond formation and speak to a pilot who saw it.
"One of the pilots goes to check out that diamond formation and sees a large, floating what I can only describe as an orb. Again, like I said, not have any human capability that I'm that aware of," Gaetz said.
Gaetz called on Pentagon officials to release that image and other details about that UAP sighting to the Oversight Committee.
ABC's Lauren Peller and Arthur Jones contributed to this report.