The US State Department has reopened an internal investigation of possible mishandling of classified information by Hillary Clinton and senior aides.
Spokesman John Kirby said the emails probe is restarting now that the Justice Department is not pursuing a criminal prosecution.
The State Department suspended its review in April to avoid interfering with the FBI's inquiry.
Mr Kirby set no deadline for the investigation's completion.
Mrs Clinton was secretary of state until early 2013, and most of her senior advisers left shortly afterwards,
But Mr Kirby said this week former officials can still face "administrative sanctions".
The most serious is loss of security clearances, which could complicate Mrs Clinton's naming of a national security team if she becomes president.
Apart from the Democratic frontrunner, the probe is most likely examining aides Cheryl Mills, Jake Sullivan and Huma Abedin.