The account was shared by Eric Taber, who claims that his late great uncle, Sam Urquhart, a former contractor at Area 51, disclosed this information in the 1980s.
Eric, a defense aerospace contractor with extensive experience and security clearance, shared his great uncle's story with the Pentagon's UFO investigation unit earlier this year.
Sam Urquhart, who served in the US Air Force from 1997 to 2014 before becoming a contractor at Area 51, allegedly witnessed the discovery of the egg-shaped UFO in the desert.
According to Eric, his great-uncle described the object as metallic, smooth, and seamless, with a silverish-grey color. It lacked control surfaces, flaps, inlets, exhaust, or any visible writing or symbols.
Engineers at Area 51 were tasked with unraveling the mysteries surrounding the craft, including its power source and activation mechanism.
Eric further revealed that his great-uncle claimed that small samples of the UFO's material were taken for analysis, leading to the conclusion that it was not of earthly origin.
Eric narrated his great-uncle's word: "These are the best and brightest engineers you can think of. They tried to no avail to figure out what the power source was, how to activate it, and how it worked.
"They tried to induce electricity to it, but X-rays couldn't penetrate it; it showed up on X-ray as a solid object. They tried to open it and penetrate its hull; they couldn't."
Eventually, the alien craft was reportedly transported to another military base, potentially the White Sands Missile Range in New Mexico, and disappeared from the engineers' knowledge.
While at work, he stumbled upon a crystal-clear color photograph of the same UFO in one of the secure data vault storage rooms within Area 51's main control building.
Former military officials who participated in a special UFO hearing in July revealed the existence of a secret US government program aimed at retrieving and analyzing non-human craft to gain technological insights from them.
Eric's testimony, along with other reports and witness statements, will be compiled by the All-domain Anomaly Resolution Office (AARO), the Pentagon's UFO investigation office, and submitted to Congress next year.
"I did this interview in a way that I feel doesn't disclose technical information our adversaries could exploit," he said in the interview.
"Despite what people may think, secrets can be kept. If you're getting paid well, if you have a security clearance, if you've signed a nondisclosure agreement, you're going to be happy, and you're going to work hard, and you're going to keep your mouth shut.
"Disclosure has to be done very carefully. We don't want our enemies to know everything about what we've got. But I do believe wholeheartedly that humanity deserves to know the truth if we have recovered these non-human objects or craft, which 100% I believe we have."