Clinton's use of a private email server has become an issue in her presidential bid. Here's what we know about the FBI's investigation, whether she could be charged with a crime and what happens next.
  1. What is the FBI investigating?
    The Justice Department and the FBI have not publicly confirmed the scope of their investigation. U.S. government sources tell NPR it involves possible mishandling of government secrets that appeared in Clinton's email messages while she worked as secretary of state. The State Department said last month it would not release 22 emails, or 37 pages in total, from Clinton's private server at the request of the intelligence community because "they contain a category of top secret information."
  2. What is Hillary Clinton saying about this?
    In an interview with NPR, Clinton said she was "absolutely not" putting top secret information at risk with her private email setup. "I took the handling of classified materials very seriously ... The emails that I received were not marked classified. Now there are disagreements among agencies on what should have been perhaps classified retroactively, but at the time that doesn't change the fact that they were not marked classified," she said.
  3. Could Clinton be charged with a crime?
    Clinton appears to reject that proposition out of hand — and she cast the controversy as part of a long-running political effort to undo her. "No absolutely not, I mean I can't prevent it from being a political case, which seems to be the motivation behind selective leaking and anonymous sourcing and the kinds of things that seem to be going on," she told NPR recently.
  4. When will the FBI investigation end?
    Federal authorities have offered no public timetable for their investigation. Typically, the Justice Department tries to avoid bringing charges too close to an election lest it influence the outcome of a political race. FBI Director James Comey has promised lawmakers he will conduct the probe quickly and independently. "We don't give a rip about politics," Comey said. He also told Republican senators that the FBI was not briefing the White House about the status of the investigation.
  5. What happens next?
    A federal judge in Washington, D.C., will hold a hearing Feb. 9, the same day as the New Hampshire primaries, on a Freedom of Information Act lawsuit by Vice News, seeking the release of Clinton emails. The State Department also has to turn over at least one more batch of her messages, a step that could come shortly before the Super Tuesday votes.