The US government says the release of the Epstein files will take "a few more weeks" after a million additional documents were uncovered.
The Trump administration has blamed the document-review process for its failure to meet a legal deadline of December 19 to release all the files.
The Department of Justice (DOJ) said lawyers were "working around the clock" preparing files for release, but the mass discovery of more documents would hold things up further.
"We will release the documents as soon as possible," the DOJ said on X.
"Due to the mass volume of material, this process may take a few more weeks."
The intermittent rollout of the documents and the ways they have been redacted have inflamed the years-long controversy around the Epstein files.
Congress passed a law last month ordering the DOJ to publish all records relating to its investigations into sex criminals Jeffrey Epstein and Ghislaine Maxwell.
The legislation permitted only limited redactions to protect victims, ongoing investigations and national security.
Victims and Democrats have voiced suspicions about the redactions that have been made, saying it appears more details have been removed than legally allowed.
Hundreds of pages were completely blacked out in the first release of files.
But at least one victim, who had been trying to keep her identity private, found her name in the documents unredacted.
"It haunts me to my core," she told CNN.
CNN also reported the DOJ had asked more staff to join the redaction effort. An email to staff acknowledged the "timing could not be worse", but asked for more lawyers to volunteer to work over the "next several days".
Robert Garcia, the top Democrat on Congress's House Oversight Committee, which has also been releasing Epstein-related materials, again accused the White House of a cover-up.
"It's outrageous that the DOJ has illegally withheld over a million documents from the public," he said in a statement.
"Every day we see lies, incompetence, missed deadlines, and illegal redactions.
"[Attorney-General] Pam Bondi needs to testify to Congress under oath to explain herself."
The new documents were found by the US Attorney for the Southern District of New York, whose office investigated and charged Epstein and Maxwell for trafficking minors.
Epstein died while awaiting trial in 2019, and Maxwell was jailed for 20 years in 2021.
'Only going to get worse' for ex-prince, biographer says
The material released so far has included photos of Epstein and his well-known associates, court records, police reports, emails, voicemail messages and flight logs.
The DOJ has said some of the documents contain "untrue and sensationalist" claims about US President Donald Trump.
Other material was fake, including a note supposedly written by Epstein to paedophile Larry Nassar, the department said.
The documents have also raised more questions about Andrew Mountbatten-Windsor, the former prince who was stripped of his royal titles because of his Epstein links.
The files show US authorities had asked the British government for assistance setting up an interview with Mr Mountbatten-Windsor back in 2020.
The FBI and prosecutors wanted to speak to the then-prince about Epstein and another accused sex trafficker, Peter Nygard. The formal request said Mr Mountbatten-Windsor was "not presently a target" of either investigation.
More recently, some Democrats have called on Mr Mountbatten-Windsor to appear before a US congressional committee, which is investigating the Epstein case.
Author Andrew Lownie, who wrote an unauthorised biography on Mr Mountbatten-Windsor, said the documents showed he had long been "batting off" requests to cooperate with authorities.
"It's very clear that he was not prepared to talk to them despite his claims in public that he was," Mr Lownie told the ABC.
"So I think this is all very damaging and it's only going to get worse."
The files also include emails between Maxwell and someone who called themself "A" of "Balmoral Summer Camp for the Royal Family".
Though the sender's identity cannot be verified, there are many details that link it to Mr Mountbatten-Windsor, who has spent dozens of summers at Scotland's Balmoral Castle.
In one 2001 email, the writer asked Maxwell, who recruited victims for Epstein: "Have you found me some new inappropriate friends?"
Mr Mountbatten-Windsor has not publicly commented on the emails, but has previously denied sexual assault allegations connected to Epstein and Maxwell.
