A federal judge Thursday ordered the State Department to begin releasing additional emails by Sept. 13 from Hillary Clinton's tenure as secretary of state that were discovered during the FBI probe into her private email server.

State Department officials confirmed the existence of the almost 15,000 emails Monday, and predicted they would need until Oct. 14 to review the emails to determine which were work-related, The Hill reported.

The order, first reported by Reuters, comes in response to a lawsuit by Judicial Watch, a conservative watchdog group.

“It is astonishing that Hillary Clinton tried to delete and hide Benghazi emails and documents. No wonder federal courts in Florida and DC are ordering the State Department to stop stalling and begin releasing the 14,900 new Clinton emails,”  Judicial Watch President Tom Fitton said in a statement.

Clinton is also expected to get a set of written questions on her email server soon from Judicial Watch. 

The newest batch of emails includes messages Clinton did not voluntarily turn over to the State Department last year but that were uncovered by the FBI during its investigation into her use of a private email server. 

The FBI concluded its investigation of Clinton's use of a private server last month, with FBI Director James Comey confirming publicly that 110 classified emails were sent and received by Clinton, as well as 2,000 that were classified after the fact.

Comey said investigators found at least three emails that contained classified markings, adding that the Democratic presidential nominee was "extremely careless." However, he did not recommend criminal charges, and the Justice Department closed the case.

However, the email issue has continued to dog her presidential campaign, with Republican rival Donald Trump commenting on her email use frequently on the campaign trail.