It was Donald Trump himself who made public the search of his home in Mar-a-Lago, Florida.
In a statement Monday night, he wrote that these were "dark times for our country."
His "beautiful home" was "besieged" and "occupied" by FBI officials.
The raid was an "attack by the radical left-wing Democrats who desperately want to prevent me from running in the presidential election again in 2024".
America is a third world country, "corrupt like never before".
Trump did not comment on the reasons for the investigation.
However, he claimed to have worked with the relevant state authorities.
The raid was therefore "not necessary or appropriate", he wrote in the social network he founded "Truth Social".
Sofia Dreisbach
North American political correspondent based in Washington.
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The searches have not yet been officially confirmed.
But according to those familiar with the case who speak out in American media, the files and documents - some of them classified - that Trump took from the White House after the end of his presidency instead of giving them to the National Archives.
Trump had already handed over 15 boxes of such documents to the archive from Mar-a-Lago earlier this year, including official correspondence between Trump and foreign heads of state.
Searching a former President's estate is highly unusual and requires high-level approvals from the Justice Department.
A spokeswoman for Attorney General Merrick Garland declined to comment on the process;
the FBI did not comment either.
Trump speaks of "witch hunt"
Trump said investigators also broke into his safe.
He compared the search to the Watergate scandal that forced then-President Richard Nixon to resign in 1974.
Trump went on to say that now that you can see that the candidates he supports are winning the primary and that he is ahead in the polls, "they are trying to stop me and the Republican Party once again."
It's a witch hunt.
Trump is expected to announce in the coming months that he will run again in the 2024 presidential election.
CNN, citing anonymous sources, reports that the raid began early Monday morning and that officers focused primarily on Trump's office and private quarters.
Trump's attorney Christina Bobb said papers were "seized."
Trump himself was not in Mar-a-Lago on Monday, but in New York.
The White House said about President Joe Biden that he knew nothing about the raid on Trump until the media reports.
FBI Agents Association President Brian O'Hare has defended investigators who conduct court-authorized searches — but without commenting explicitly on the Trump case.
Accordingly, search warrants would be issued by federal judges and would have to follow clear rules.
They are the result of cooperation and consultation with the competent lawyers at the Ministry of Justice.
The FBI agents "are focused on upholding the law and the Constitution."
Trump had appointed the head of the FBI, Christopher Wray, himself in 2017, but probably thought about firing him several times due to disagreements.
Sharp attack from California
With less than 100 days to go before the congressional elections, the raid provides Republicans with plenty of material for the campaign and the tale of a politicized justice system.
Shortly after Trump's statement, many Republicans backed the former president.
The sharpest attack came from Republican minority leader in the House of Representatives, Kevin McCarthy from California.
He threatened the Justice Department with an investigation if Republicans regained control of the House of Representatives in November's congressional elections.
Senator Lindsey Graham of South Carolina called the investigation into a former president so close to the midterm elections "more than problematic".
Trump's son Eric said Monday night on Fox News that dealing with Trump was "political persecution."
He claimed the orders for the raid came from the Biden administration.
"It's not us.
This is Venezuela.” They are “antics of a banana republic”.
Fox News captioned a report on the raid: "Biden's FBI to ransack prospective adversary's home in 2024."