Federal investigators were made aware of the potential existence of secret materials at former US President Donald Trump's Mar-a-Lago home in Florida by an individual acquainted with the files kept there, The Wall Street Journal reported.

According to a story published late on Wednesday, FBI agents visited Mar-a-Lago, on June 3, to discuss boxes of federal documents stowed in the residence's basement a few days after, they sent a note asking for a stronger lock to be installed in the storage room.

The newspaper cited persons with knowledge of the issue as saying that weeks later, a source familiar with the documents kept at Mar-a-Lago informed investigators that more classified material may be kept there than they were aware of.

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According to the article, the National Archives retrieved 15 cartons of records from Trump earlier this year. Agents took boxes with them after FBI investigators ended their Monday raid at Mar-a-Lago, according to the article.

The raid has been denounced by Trump, who stated that "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," adding that "It is prosecutorial misconduct, the weaponization of the Justice System, and an attack by Radical Left Democrats who desperately don't want me to run for President in 2024."

The raid's warrant, which would provide the justification for the search, has not yet been made available to the public. However, a US federal court mandated on Wednesday that the government respond to a request to unseal the warrant made by the legal advocacy group Judicial Watch by August 15.

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