FBI Found 15,000 More Clinton Emails

The FBI uncovered nearly 15,000 more emails and materials sent to or from Hillary Clinton as part of the agency's investigation into Clinton's use of private email at the State Department.

The documents were not among the 30,000 work-related emails turned over to the State Department by Clinton's attorneys in December 2014.

The State Department confirms it has received "tens of thousands" of personal and work-related email materials -- including the 14,900 emails found by the FBI -- that it will review.

The number of emails provided by the FBI to the State Department for review is much higher than the "several thousand" that FBI Director James Comey said in July had been uncovered as part of his agency's investigation.

"We found those additional emails in a variety of ways," Comey explained in July. "Some had been deleted over the years and we found traces of them on devices that supported or were connected to the private e-mail domain. Others we found by reviewing the archived government e-mail accounts of people who had been government employees at the same time as Secretary Clinton...still others we recovered from the laborious review of the millions of e-mail fragments dumped into the slack space of the server decommissioned in 2013."

The State Department committed last week to publicly release the emails uncovered by the FBI as part of a pre-existing freedom of information lawsuit brought by the conservative watchdog group, Judicial Watch.

At a status hearing Monday before federal Judge Emmett Sullivan, who is overseeing that case, the State Department presented a schedule for how it would release the emails found by the FBI.

The first group of emails -- 14,900 -- was ordered released and a status hearing on Sept. 23 "will determine the release of the new emails and documents," Sullivan said.

"As we have previously explained, the State Department voluntarily agreed to produce to Judicial Watch any emails sent or received by Secretary Clinton in her official capacity during her tenure as Secretary of State which are contained within the material turned over by the FBI and which were not already processed for FOIA by the State Department," said State Department spokesman Mark Toner in a statement issued Monday.

"We can confirm that the FBI material includes tens of thousands of non-record (meaning personal) and record materials that will have to be carefully appraised at State," said Toner.

The FBI uncovered the documents as part of its investigation into Clinton's use of private email at the State Department.

"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" said Toner, declining further comment.

At his July news conference announcing his recommendation that no criminal charges should be filed against Clinton, Comey disclosed that investigators had found "several thousand work-related emails that were not in the group of 30,000 that were returned by Secretary Clinton to State in 2014."

Three of these several thousand emails were classified at the time they were sent or received, Comey said.

ABC News' Mike Levine contributed to this story.