Presidential hopeful Hillary Clinton was interviewed by the FBI on Saturday about her alleged use of a private unsecured email server to send or receive government material.
Clinton campaign spokesman Nick Merrill said in a statement the interview with federal agents about her email use when she was Secretary of State was voluntary.
The interview was not unexpected and does not suggest that Clinton is likely to face prosecution.
At the beginning of the year, the US government confirmed that Clinton's home internet sever contained 22 emails with material that was top secret.
The Democrat candidate has insisted she never sent or received information on her personal email account that was classified at the time.
Legal experts say that criminal prosecution is exceedingly unlikely and the interview may indicated the Justice Department's year-long probe is drawing to a close.