Previous releases of Epstein documents have included revelations that reverberated across the Atlantic. Photo: BBC

The FBI and federal prosecutors in New York informed the Department of Justice (DoJ) of the discovery.

"We have lawyers working around the clock to review and make the legally required redactions to protect victims, and we will release the documents as soon as possible," the DoJ said on Wednesday.

The department said it could take "a few more weeks" before all the files are released. The DoJ has been under scrutiny after not releasing all Epstein files by 19 December, the deadline mandated under a new law.

The agency said it would "continue to fully comply with federal law and President Trump's direction to release the files".

The statement did not specify how the FBI and the US Attorney for the Southern District of New York came across the additional material. Epstein had been facing charges of sex trafficking minors in the state when he died awaiting trial in a New York prison.

The news comes after the justice department released thousands of documents - some heavily redacted - related to their investigations into Epstein.

The department has been releasing the documents in batches and top officials have said hundreds of thousands of documents still are to be released.

The files were released after Congress passed the Epstein Files Transparency Act - signed into law by US President Donald Trump - that ordered the agency to share all the documents with the public while protecting victims' identities.

Many of the released documents, which include videos, photos, emails and investigative documents, have heavy redactions, including names of people the FBI appears to cite as possible co-conspirators in the Epstein case.

The justice department has faced criticism from lawmakers on both sides of the aisle over the amount of redactions, which the law permits only to protect victims' identities and active criminal investigations.

In a post on X after the discovery of the additional documents was announced, the top Democrat on the House Oversight Committee, a congressional panel that has been investigating the Epstein saga, accused the White House of “illegally” withholding the files.

“Every day we see lies, incompetence, missed deadlines, and illegal redactions,” Representative Robert Garcia said in a statement.

The law passed by Congress and signed last month by Trump states that names and information that might be embarrassing or cause "reputational harm" are not allowed to be redacted.

It specifically asks the DoJ for internal communications and memos detailing who was investigated and decisions on whether "to charge, not charge, investigate, or decline to investigate Epstein or his associates".

Included in the documents are emails appearing to be exchanged between FBI personnel in 2019 that mention 10 possible "co-conspirators" of Epstein.

The emails said six of the group had been served with subpoenas. This included three in Florida, one in Boston, one in New York City, and one in Connecticut.

Possible co-conspirators in Epstein's crimes are a major focus for his victims, and for several lawmakers who have demanded more transparency from the justice department.

Previous releases of Epstein documents have included revelations that reverberated across the Atlantic.