Trump once boasted about secret nuclear weapon technology, according to Bob Woodward.
The president told Woodward in 2019 about the secret system, according to the 2020 book "Rage."
The FBI was looking for documents relating to nuclear weapons during its search of Mar-a-Lago this week, the Washington Post reported.
Donald Trump once boasted to a reporter about the nuclear information he had.
In Bob Woodward's 2020 book "Rage," the journalist detailed a conversation with Trump in 2019 in which the then-president described a secret nuclear weapons system he credited himself with creating.
"I have built a nuclear - a weapons system that nobody's ever had in this country before. We have stuff that Putin and Xi have never heard about before. There's nobody - what we have is incredible," Trump reportedly said.
Woodward wrote that sources confirmed the new weapons system existed, but were "surprised Trump had disclosed it."
It's not clear what kind of nuclear weapons Trump was referring to.
FBI agents descended on Donald Trump's Mar-a-Lago home to carry out a search warrant on Monday.
The Justice Department has not confirmed what investigators were looking for, but The Washington Post reported that documents related to nuclear information were among the items that federal agents had their sights on.
Trump called the reports of nuclear weapons documents being among the items in the search warrant "a hoax."
"Nuclear weapons issue is a Hoax, just like Russia, Russia, Russia was a Hoax, two Impeachments were a Hoax, the Mueller investigation was a Hoax, and much more," Trump posted on his social media site Truth Social.
But he later didn't deny that he had nuclear documents at Mar-a-Lago, instead attacking former President Barack Obama.
Trump falsely accused Obama of illegally keeping classified documents.
"President Barack Hussein Obama kept 33 million pages of documents, much of them classified," Trump wrote on his Truth Social platform. "How many of them pertained to nuclear? Word is, lots!"
But unlike Trump, Obama had his records processed by the National Archives before having them transferred to his presidential library in Chicago, Insider's Nicole Gaudiano and Sonam Sheth previously reported.