The FBI searched Donald Trump's Mar-a-Lago estate as part of an investigation into whether he took classified records from the White House to his Florida residence, people familiar with the matter said Monday, a move that represents a dramatic and unprecedented escalation of law enforcement scrutiny of the former president.

Trump, disclosing the search in a lengthy statement, asserted that agents had opened up a safe at his home and described their work as an “unannounced raid” that he likened to “prosecutorial misconduct.”

The search intensifies the months-long probe into how classified documents ended up in boxes of White House records located at Mar-a-Lago earlier this year. It occurs amid a separate grand jury investigation into efforts to overturn the results of the 2020 presidential election and adds to the potential legal peril for Trump as he lays the groundwork for another run.

Familiar battle lines, forged during a a four-year presidency shadowed by FBI and congressional investigations, quickly took shape again Monday night. Trump and his allies sought to cast the search as a weaponization of the criminal justice system and a Democratic-driven effort to keep him from winning another term in 2024 - even though the Biden White House said it had no prior knowledge of it, and the current FBI director, Christopher Wray, was appointed by Trump five years ago and served as a high-ranking official in a Republican-led Justice Department.

“These are dark times for our Nation, as my beautiful home, Mar-A-Lago in Palm Beach, Florida, is currently under siege, raided, and occupied by a large group of FBI agents,” Trump wrote. “Nothing like this has ever happened to a President of the United States before.”

“After working and cooperating with the relevant Government agencies, this unannounced raid on my home was not necessary or appropriate,” Trump said in his statement.

Justice Department spokesperson Dena Iverson declined to comment on the search, including about whether Attorney General Merrick Garland had personally authorized it.

Trump did not elaborate on the basis for the search, but the Justice Department has been investigating the potential mishandling of classified information after the National Archives and Records Administration said it had received from Mar-a-Lago 15 boxes of White House records, including documents containing classified information, earlier this year. The National Archives said Trump should have turned over that material upon leaving office, and it asked the Justice Department to investigate.

There are multiple federal laws governing the handling of classified records and sensitive government documents, including statutes that make it a crime to remove such material and retain it at an unauthorized location. Though a search warrant does not suggest that criminal charges are near or even expected, federal officials looking to obtain one must first demonstrate to a judge that they have probable cause that a crime occurred.

Two people familiar with the matter, who spoke on condition of anonymity to discuss an ongoing investigation, said the search happened earlier Monday and was related to the records probe. Agents were also looking to see if Trump had additional presidential records or any classified documents at the estate.

Trump has previously maintained that presidential records were turned over “in an ordinary and routine process.” His son Eric said on Fox News on Monday night that he had spent the day with his father and that the search happened because “the National Archives wanted to corroborate whether or not Donald Trump had any documents in his possession.”

Asked how the documents ended up at Mar-a-Lago, Eric Trump said the boxes were among items that got moved out of the White House during “six hours” on Inauguration Day, as the Bidens prepared to move into the building.

“My father always kept press clippings,” Eric Trump said. “He had boxes, when he moved out of the White House.”

Trump emerged from Trump Tower in New York City shortly before 8 p.m. and waved to bystanders before being driven away in an SUV.

In his first public remarks since news of the search surfaced, Trump made no mention of it during a tele-town hall on behalf of Leora Levy, the Connecticut Republican he has endorsed in Tuesday’s U.S. Senate primary to pick a general election opponent against Democratic U.S. Sen. Richard Blumenthal. Trump gave his public backing to Levy late last week, calling her on Monday the best pick “to replace Connecticut’s joke of a senator.”

But in a social media post Monday night, he was much more unguarded, calling the search a “weaponization of the Justice System, and an attack by Radical Left Democrats who desperately don’t want me to run for President in 2024.”

Other Republicans echoed that message. GOP National Committee Chair Ronna McDaniel denouncing the search as “outrageous” and said it was a reason for voters to turn out in November.

Florida Gov. Ron DeSantis, a Republican who is considered a potential 2024 presidential candidate, said in a statement on Twitter that it was “an escalation in the weaponization” of U.S. government agencies. Kevin McCarthy, the House Minority Leader, said in a tweet that the Justice Department “has reached an intolerable state of weaponized politicization” and said that if Republicans win control of the U.S. House, they will investigate the department.

That Trump would become entangled in a probe into the handling of classified information is all the more striking given how he tried during the 2016 presidential election to exploit an FBI investigation into his Democratic opponent, Hillary Clinton, over whether she mishandled classified information via a private email server she used as secretary of state. Then-FBI Director James Comey concluded that Clinton had sent and received classified information but the FBI did not recommend criminal charges because it determined that Clinton had not intended to break the law.

Trump lambasted that decision and then stepped up his criticism of the FBI as agents began investigating whether his campaign had colluded with Russia to tip the 2016 election. He fired Comey during that probe, and though he appointed Wray months later, he repeatedly criticized him too as president.

Thomas Schwartz, a Vanderbilt University history professor who studies and writes about the presidency, said there is no precedent for a former president facing an FBI raid -- even going back to Watergate. President Richard Nixon wasn’t allowed to take tapes or other materials from the White House when he resigned in 1974, Schwartz noted, and many of his papers remained in Washington for years before being transferred to his presidential library in California.

“This is different and it is a sign of how unique the Trump period was,” said Schwartz, author of “Henry Kissinger and American Power: A Political Biography.” “How his behavior was so unusual.”

The probe is hardly the only legal headache confronting Trump. A separate investigation related to efforts by Trump and his allies to undo the results of the 2020 presidential election - which led to the Jan. 6, 2021, riot at the U.S. Capitol - has also been intensifying in Washington. Several former White House officials have received grand jury subpoenas.

And a district attorney in Fulton County, Georgia, is investigating whether Trump and his close associates sought to interfere in that state's election, which was won by Democrat Joe Biden.