FBI agents in this week's search of former US President Donald Trump's Florida home removed 11 sets of classified documents, including some marked top secret, according to the Justice Department, which also disclosed probable cause to conduct the search based on possible violations of the Espionage Act.

The explosive revelations were made in a search warrant authorized by a US magistrate court, and accompanying documents disclosed four days after officers investigated Trump's Mar-a-Lago estate in Palm Beach.

The Espionage Act, one of three crimes referenced in the warrant application, was enacted in 1917 and made it illegal to disclose information that could compromise national security.

Trump tweeted on his social media channel that the documents had been "completely declassified" and placed in "secure storage."

"They were not required to seize anything. Without playing politics and breaking into Mar-a-Lago, they could have had it whenever they wanted, the Republican businessman-turned-politician added.

The search was conducted as part of a federal inquiry into whether Trump removed papers illegally when he left office in January 2021 after losing the presidential election to Democrat Joe Biden two months earlier.

Even though the FBI removed classified materials on Monday, the three laws mentioned as the basis for the warrant make it illegal to mishandle federal information regardless of their classification. As a result, Trump's assertions that he declassified the records are irrelevant to the alleged legal infractions.

A list of materials revealed that FBI agents released more than 30 items, including more than 20 boxes, photo albums, a handwritten message, and the executive clemency granted to Trump confidant and longtime adviser Roger Stone. The list also featured information about the "French President."

The warrant said that FBI agents were instructed to examine a room known as "the 45 Office" Trump was the 45th president of the United States, as well as any other rooms, structures, or buildings on the estate used by Trump or his staff for storing boxes or documents.

In the warrant application issued by US Magistrate Judge Bruce Reinhart, the Justice Department stated that it had probable cause to think that violations of the Espionage Act had occurred at Trump's residence.

This statute was initially enacted to prevent espionage. Before the Justice Department's increased use of the statute under Trump and his predecessor, Barack Obama, prosecutions for leaking national security secrets, including to the media, were relatively rare.

The part of the legislation invoked to justify the warrant forbids the unlawful possession of national defense information. It did not specify why investigators have probable cause to suspect such a violation happened.

In recent years, the Justice Department has utilized the Espionage Act in several high-profile cases, including former National Security Agency contractor Edward Snowden, former military intelligence analyst Chelsea Manning, and WikiLeaks founder Julian Assange.

The application also alleged violations of two other laws that make it illegal to conceal or destroy official US records.

-Classification levels- There are three primary classification levels for sensitive government documents: top secret, secret, and confidential.

"Top secret" is the highest classification, designated for the most sensitive national security information of the United States. Such records are often stored in secure government facilities, as their revelation might severely compromise national security.

It was revealed that on Monday, the FBI agents gathered four sets of top-secret papers, three sets of secret documents, and three sets of confidential documents. It was found that agents had amassed a collection of documents labeled "classified/TS/SCI documents," a reference to classified and compartmented sensitive information.

Donald Trump has not been accused of any misconduct. It was unknown whether any charges would be filed.

An escalation

Monday's search marked a significant escalation in one of the numerous federal and state investigations he faces from his time in office and private business, including a separate investigation by the Justice Department into a failed attempt by Trump's allies to overturn the 2020 presidential election by submitting fake slates of electors.

Trump refused to answer questions during a civil inquiry of his family's business operations before the attorney general of New York state on Wednesday, citing his constitutional privilege against self-incrimination.

Thursday, Attorney General Merrick Garland revealed that the department had requested Reinhart to unseal the warrant. This followed Trump's assertion that the search was political retaliation and his unfounded accusation that the FBI may have planted evidence against him.

According to legal experts, Trump's assertion that he declassified the documents would not be an effective defense should he ever face criminal charges.

Heidi Kitrosser, a law professor at Northwestern University, stated about the Espionage Act, "the statute does not strictly require that the information be classified so long as it relates to national defense."

The inquiry into Trump's removal of public records began this year when the National Archives and Records Administration referred the matter to the Justice Department. The National Archives and Records Administration is entrusted with protecting presidential public records.

Friday, Republican members of the House Intelligence Committee demanded that Garland and FBI Director Chris Wray reveal the affidavit supporting the request, arguing that the public has a right to know.

Representative Michael Turner, the leading Republican on the committee, told reporters, "Because they had many other options available to them, we're very concerned about the method used to raid Mar-a-Lago."

Turner noted that if the affidavit remains sealed, "it will still leave many questions unanswered."

The Justice Department's move to unseal the warrant did not include a request to unseal the accompanying affidavit and Trump's legal team has not made a similar argument in public.

Since Monday's search, the department has been the target of harsh criticism and internet threats, which Garland has condemned.

Trump's fans and some Republicans in Washington have accused Democrats of using the federal bureaucracy as a weapon against him as he considers a 2024 presidential candidacy.