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, AP reported.

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 more than a dozen boxes 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.

“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.

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 retrieved from Mar-a-Lago 15 boxes of records 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.

Two people familiar with the matter 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.”

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.