FBI raid on Trump's beachside estate: What we know

The FBI raid on former US president Donald Trump's beachside Mar-a-Lago estate in Palm Beach, Florida was unprecedented and stunned America.

But facts about the raid and what lay behind it remain sparse. Here's what we know and what questions remain unanswered:

On Monday morning a group of FBI agents -- around 30, claimed Trump's son Eric -- arrived at the palatial Mar-a-Lago. Trump was staying in New Jersey at the time.

It was not a forceful raid, as the agents notified the Secret Service, which protects the former president, before their arrival, according to NBC.

Once inside they searched the premises for hours, including opening a safe. Politico, citing a person familiar with the events, said the agents took away "paper records."

"Nothing like this has ever happened to a president of the United States before," Trump said in a statement, calling the raid "not necessary or appropriate."

The Justice Department and FBI have stayed silent on the investigation.

Experts said that a raid directed at Trump, who could seek the presidency again in 2024, was such a politically fraught move it had to be approved by Attorney General Merrick Garland and FBI Director Christopher Wray.

The FBI would have needed a warrant, which would require a judge's review of their justification for pushing into an ex-president's home.

But the warrant, which could reveal the nature of the investigation, remains secret.

Seamus Hughes deputy director of the Program on Extremism at George Washington University and an expert on court filings, said the federal prosecutor in southern Florida by practice keeps warrants sealed.

"Each court district can set their own local rules for public access to documents," he said.

Eric Trump told Fox News that the raid was linked to allegations over large amount of documents the president took with him when he exited the White House in January 2021.

Early this year he was forced to turn over 15 boxes of those documents to the National Archives, which controls presidential records.

The Archives later reported to the Justice Department that the boxes included some highly classified documents.

The raid suggested there were more such records in Mar-a-Lago.

"The purpose of the raid, from what they said, was because the National Archives wanted to corroborate whether or not Donald Trump had any documents in his possession," Eric Trump said.

The Presidential Records Act says all records related to official business must be turned over to the Archives. But violating the act brings little consequence.

On the other hand, US law strictly forbids people retaining classified documents, and carries stiff prison sentences.

One indication that the investigation could involve classified materials was a visit to Mar-a-Lago in June by the chief of the Justice Department's Counterintelligence and Export Control Section, according to CNN.

That section oversees cases affecting national security, like espionage and sabotage, as well as cases involving Americans who lobby for foreign governments.

The raid itself doesn't necessarily mean Trump is under investigation for a crime.

The records sought could be required in other investigations involving members of his administration, including for the probe into the January 6, 2021 attack on Congress by hundreds of Trump supporters.

But the nature of the raid, analysts say, suggests something much more weighty.

Former FBI deputy director Andrew McCabe told CNN he didn't believe it was simply about National Archives materials.

"The idea that they would do this simply because they were not getting the sort of compliance they were looking for... seems really unimaginable to me. It seems like they must have more than just that."