US Federal prosecutors have notified former president Donald Trump's lawyers that he is the target of an investigation into his handling of classified materials, a person familiar with the matter said, adding to his legal troubles as he campaigns for the White House in 2024.

The Justice Department typically notifies people when they become targets of an investigation to give them an opportunity to present their own evidence before a grand jury.

The notification does not necessarily mean Mr Trump will be charged.

News of the notification to Mr Trump's legal team surfaced just two days after his attorneys met with Justice Department officials to discuss the case.

Mr Trump's legal team was notified on Monday, the person said.

Although there are some signs that the documents investigation is coming to a close, the timing of when a person is told they are a target cannot necessarily be used as a predictor of when charges might be brought, said David Schoen, an attorney who represented Trump ally Steve Bannon during his criminal trial on contempt of Congress charges.

"Sometimes they are issued at the beginning of a long investigation and sometimes at the conclusion of an investigation," he said.

Mr Trump, the front-runner in the race for the 2024 Republican presidential nomination, has repeatedly described the multiple investigations as politically motivated.

A federal grand jury has been investigating his retention of classified materials after leaving the White House in 2021.

A second criminal investigation is looking into alleged efforts by Mr Trump and his allies to overturn his 2020 election loss to Democrat Joe Biden.

A spokesperson for Special Counsel Jack Smith, who is leading the investigations, declined to comment.

Investigators in August 2022 seized roughly 13,000 documents from Mr Trump's Mar-a-Lago estate in Palm Beach, Florida. One hundred of these were marked as classified, even though one of Mr Trump's lawyers had previously said that all records with classified markings had been returned.

Mr Trump has defended his retention of documents, suggesting that he declassified them while he was president. However, Mr Trump has not provided evidence of this and his attorneys have not made that argument in court filings.

Mr Trump is the first current or former US president to face criminal charges, having pleaded not guilty in April to felony charges for allegedly falsifying business records relating to hush money paid to an adult film actress before the 2016 presidential race.

Mr Trump handed over 15 boxes of records in January 2022, a year after leaving office, but federal officials came to believe he had not returned all the documents.

The Justice Department issued Mr Trump a grand jury subpoena in May 2022 asking him to return any other records bearing classified markings, and top officials travelled to Mar-a-Lago to retrieve the materials.

Mr Trump's attorneys turned over 38 pages marked as classified to FBI and Justice Department officials and showed them a storage room at Mar-a-Lago, but did not permit the agents to open any of the boxes.

One of Mr Trump's lawyers also signed a document attesting that all records with classified markings had been returned to the government - a claim later proven false after the FBI searched his home.

Mr Trump's legal woes are growing.

A jury in federal court in Manhattan in May decided in a civil lawsuit that Mr Trump must pay $5 million in damages for sexually abusing former Elle magazine columnist E Jean Carroll and then defaming her by branding her a liar.

Mr Trump also faces a criminal investigation by a county prosecutor in Georgia relating to his efforts to undo his 2020 election loss in that state.