The US has been asked to provide UFO proof after a whistleblower former intelligence official said the government possessed "intact and partially intact" alien vehicles.

Former intelligence official David Grusch, who oversaw the investigation of unexplained anomalous phenomena (UAP) inside a US Department of Defense agency, claimed that the US has craft of non-human origin, reports The Guardian.

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According to Grusch, information on these vehicles is being illegally hidden from Congress. Grusch said he faced reprisal from federal authorities after turning over secret information regarding the vehicles to Congress. After a 14-year career in US intelligence, he retired in April, it said.

Jonathan Grey, a current US intelligence official at the National Air and Space Intelligence Center (Nasic), told the Debrief that "exotic materials" existed, adding, "We are not alone."

The revelations come after a surge of genuine sightings and claims have reignited interest in extraterrestrial spacecraft, and maybe visits, in recent years, said the report.

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In 2021, the Pentagon issued a report on UAPs -- the name favoured by many of the extraterrestrial world over UFOs -- that mentioned more than 140 cases of UAP encounters that could not be explained.

The revelation came after a release of military film showing seemingly odd events in the sky, and naval pilots testified that they had routinely encountered strange craft off the US coast, the report also said.

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Grusch stated that the US government and defense contractors had been recovering fragments of non-human craft, and in some cases entire craft, for decades in an interview with Debrief journalists Leslie Kean and Ralph Blumenthal, who previously exposed the existence of a secret Pentagon program that investigated UFOs.

“We are not talking about prosaic origins or identities,” Grusch said. “The material includes intact and partially intact vehicles.”

According to Grusch, examination indicated that this material is "of exotic origin" -- meaning "non-human intelligence, whether extraterrestrial or unknown in origin."

“[This assessment is] based on the vehicle morphologies and material science testing and the possession of unique atomic arrangements and radiological signatures,” Grusch said.

According to the Debrief, Grey, who investigates unexplained anomalous events inside the Nasic, validated Grusch's claim.

“The non-human intelligence phenomenon is real. We are not alone,” Grey said. “Retrievals of this kind are not limited to the United States. This is a global phenomenon, and yet a global solution continues to elude us.”

The Debrief met with numerous of Grusch's former coworkers, all of whom spoke well of him. Grusch was described as "beyond reproach" by former army colonel Karl E Nell. Grusch was hailed as "an officer with the strongest possible moral compass" in a 2022 performance assessment obtained by the Debrief.

Nick Pope, who worked for the British Ministry of Defence (MoD) studying UFOs in the early 1990s, called Grusch and Grey's claim of extraterrestrial elements "very significant."

“It’s one thing to have stories on conspiracy blogs, but this takes it to the next level, with genuine insiders coming forward,” Pope said.

“When these people make these formal complaints, they do so on the understanding that if they’ve knowingly made a false statement, they are liable to a fairly hefty fine, and/or prison.

“People say: ‘Oh, people make up stories all the time.’ But I think it’s very different to go before Congress and go to the intelligence community inspector general and do that. Because there will be consequences if it emerges that this is not true.”