Hillary Clinton met with the Federal Bureau of Investigation on Saturday morning for a "voluntary interview" about the investigation into her use of a private email server while serving as secretary of state, her campaign announced.

The interview at FBI headquarters in Washington, which lasted for three and a half hours according to a campaign aide, is a long-expected development in the months-long email saga that has complicated Clinton's White House bid since before its formal inception. Clinton has steadfastly denied any wrongdoing and pledged to cooperate with bureau's inquiry, bluntly telling an interviewer in March that an indictment is "not going to happen."