Newly released documents from the State Department reveal Hillary Clinton was the subject of a grand jury investigation related to her BlackBerry email accounts.

The conservative watchdog group Judicial Watch revealed on Friday that FBI Special Agent E.W. Priestap made a declaration stating the former secretary of state was under investigation for using a private email account on her BlackBerry.

The documents were produced in response to Judicial Watch's lawsuit looking to force Secretary of State Rex Tillerson to take action in recovering emails from Clinton and other State Department employees. The lawsuit was originally filed against former Secretary of State John Kerry on April 30, 2015, after the State Department refused to take action on a letter notifying him about the "unlawful removal of the Clinton emails."

"In the filing Priestap declares under penalty of perjury that the FBI ‘obtained Grand Jury subpoenas related to the Blackberry e-mail accounts, which produced no responsive materials, as the requested data was outside the retention time utilized by those providers,'" Judicial Watch reported.

Clinton and her top aides used an unsecured email server and a private email account to conduct official State Department business during her tenure.