The presidential hopeful is said to have been interviewed for more than three hours yesterday
Hillary Clinton has said she was 'eager' to talk to the FBI about her use of a private email server while she was Secretary of State.
Clinton has previously apologised for using a private account exclusively from her upstate New York home during her four years as America's top diplomat.
She handed over 30,000 of the emails to the State Department, but deleted another 30,000 which she said were "personal".
Yesterday, the presumptive Democratic presidential candidate's campaign said the "voluntary" meeting with federal agents took place on Saturday.
The interview took place at the FBI headquarters in Washington DC and lasted three and a half hours.
Speaking to NBC News' Chuck Todd yesterday, the presumptive Democratic candidate said: "I've been eager to do it and I was pleased to have the opportunity to assist the department in bringing its review to a conclusion.
"Let me just repeat what I have repeated for many months now: I never received nor sent any material that was marked classified," she added.
The FBI interview does not mean she will face criminal prosecution, a scenario most legal experts deem highly improbable.
Yesterday's interview came only weeks before she is due to formally accept her party's presidential nomination at the Democratic national convention.
The scandal has dogged her campaign for more than a year and has helped feed opponents' arguments that she is not trustworthy.
Critics say her private email breached rules about protecting classified documents from cyber attack and may have amounted to a crime.
Presumptive Republican candidate Donald Trump has regularly criticised Clinton over the issue, and yesterday tweeted that "what she did was wrong":
It is impossible for the FBI not to recommend criminal charges against Hillary Clinton. What she did was wrong! What Bill did was stupid!— Donald J. Trump (@realDonaldTrump) July 2, 2016