The unprecedented search of a former president's home would mark a significant escalation into the records investigation, which is one of several probes Trump is facing from his time in office and in private business.
The US Justice Department declined to comment on the search, which Trump in a statement said involved a "large group of FBI agents".
The FBI's headquarters in Washington and its field office in Miami both declined comment.
Eric Trump, one of the former president's adult children, told Fox News the search concerned boxes of documents that Trump brought with him from the White House, and that his father has been co-operating with the National Archives on the matter for months.
A source familiar with the matter also confirmed to Reuters the raid appeared to be tied to Trump's removal of classified records from the White House.
Trump said the estate "is currently under siege, raided, and occupied". He did not say why the raid took place.
"After working and co-operating with the relevant government agencies, this unannounced raid on my home was not necessary or appropriate," Trump said, adding: "They even broke into my safe!"
Trump was not present at the time as he was in New York on Monday, Fox News Digital reported, publishing a photo of Trump that a Fox reporter said showed him leaving Trump Tower.
Trump, who has made his club in Palm Beach his home since leaving the White House in January 2021, has generally spent summers at his golf club in Bedminster, New Jersey, because Mar-a-Lago typically closes for the summer.
A federal law called the US Presidential Records Act requires the preservation of memos, letters, notes, emails, faxes and other written communications related to a president's official duties.
Any search of a private residence would have to be approved by a judge, after the investigating law-enforcement agency demonstrated probable cause that a search was justified.
It almost certainly would also be approved by FBI Director Christopher Wray, a Trump appointee, and his boss, Attorney-General Merrick Garland, who was appointed by Trump's successor and political rival, President Joe Biden.
Democratic supporters of Biden have criticised Garland for being overly cautious in investigating Trump over his attempts to overturn his 2020 election loss to Biden.
But Trump supporters in turn have accused the Democrats of weaponising the federal bureaucracy to target Trump, even as Biden has taken steps to distance himself from the Justice Department.
Republicans including national committee chair Ronna McDaniel, House Minority Leader Kevin McCarthy and Florida Governor Ron DeSantis denounced the search on Monday.
McCarthy tweeted that the Justice Department "has reached an intolerable state of weaponized politicization" and if Republicans won control of the US House, they would investigate the department.
In February, Archivist David Ferriero told US House lawmakers that the National Archives and Records Administration had been in communication with Trump throughout 2021 about the return of 15 boxes of records. He eventually returned them in January 2022.
Trump previously confirmed that he had agreed to return certain records to the archives, calling it "an ordinary and routine process". He also claimed the archives "did not 'find' anything".
Trump is under investigation on a number of other fronts, including a congressional probe into the January 6, 2021, assault by Trump supporters on the US Capitol and accusations that Trump tried to influence Georgia's 2020 election results.
In addition, the US Attorney in Washington, DC, is probing a scheme by Trump's allies to submit slates of fake electors in a failed bid to overturn the 2020 presidential election.
Reuters with AP
