U.S FBI has uncovered nearly 15,000 previously undisclosed documents in Hillary Clinton email prob

Bill and Hillary Clinton

The U.S. Federal Bureau of Investigation (FBI) has uncovered nearly 15,000 previously undisclosed documents to or from Democratic presidential nominee Hillary Clinton when she served as secretary of state; a federal judge was told at a hearing on Monday.

Lawyers for the State Department suggested beginning the release of the emails weekly on Oct. 14 in a civil public records lawsuit before U.S. District Judge James E. Boasberg of Washington.

However, Boasberg rejected the proposal, ordering the State Department to prioritise Clinton's emails and to return to court on Sept. 22 with a new plan.

Tom Fitton, president of the conservative legal group Judicial Watch, which filed the lawsuit in May 2015 after disclosures that Clinton had exclusively used a personal email server based at her home when she worked with the State Department, welcomed the judge's decision.

"We're pleased the court accelerated the State Department's timing," said Fitton, accusing the State Department of having slow-walked and stonewalled the release of these records.

"they've had many of them since July 25 ... and not one record has yet been released, and we don't understand why that's the case." he said.

The Judicial Watch has been seeking all emails sent or received by Clinton at the State Department in a request made under the federal Freedom of Information Act.

State Department spokesman Mark Toner argued that tens of thousands of emails to or from Clinton would have to be "carefully appraised at State" to separate official records from personal ones before handing over.

"State has not yet had the opportunity to complete a review of the documents to determine whether they are agency records or if they are duplicative of documents State has already produced through the Freedom of Information Act," Toner said in a written statement.

The amount of the newly uncovered documents is almost half of the roughly 30,000 work-related documents that Clinton's lawyers turned over to the State Department in 2014.

The State Department previously agreed voluntarily to hand over emails to or from Clinton in her official capacity as Secretary of State from 2009 to 2013.

After a yearlong probe, the Justice Department closed a criminal probe in July with no charges into the handling of classified material in Clinton's email setup, which FBI Director James B. Comey reproached "extremely careless."