Now that criminal charges are off the table in the investigation of former Secretary of State Hillary Clinton’s e-mails, the US State Department is taking up its own investigation once again, looking into the mishandling of classified information by Clinton, her staff, and other State Department employees who forwarded classified information via State’s unclassified e-mail system. According to the Associated Press, State Department spokesperson John Kirby said that State had held up its own review, started in January, until the completion of the FBI investigation.

While Clinton’s core staff left the department shortly after she did, the State investigation could have material impact on the future careers of Clinton chief of staff Cheryl Mills, and deputy chiefs of staff Jacob Sullivan and Huma Abedin—including the revocation of security clearances and blocking of any future access to a security clearance. The actions would be kept on file, Kirby said; they could block them from top jobs if Clinton is elected president. Sullivan has been said to have been a top candidate for the position of National Security adviser in a Clinton administration. Some of Clinton’s former State staff still hold security clearances, according to reports.

All three sent information later determined to be classified—some of it as highly as Top Secret /Sensitive Compartmented Information (TS/SCI) via State’s unclassified e-mail system to Clinton’s private, unsecured e-mail server. But as revealed during a hearing of the House Oversight Committee Thursday, as many as 1,000 State Department employees were connected to classified information sent through the unclassified e-mail system that found its way into Clinton’s server—almost all of it unmarked with classification information, and some of it including information about CIA and other Intelligence Community personnel and assets overseas.

"We will aim to be as expeditious as possible, but we will not put artificial deadlines on the process," Kirby told AP’s Bradley Klapper. "Our goal will be to be as transparent as possible about our results, while complying with our various legal obligations."

The potential legal woes for Clinton are also not over. House Oversight Committee chairman Rep. Jason Chaffetz (R-Utah) said Thursday that Congress would be making a referral to the FBI to investigate whether Clinton perjured herself during testimony in which she claimed she had not sent or received any classified e-mails from her private mail server account.