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Presumptive Democratic nominee Hillary Clinton was questioned by the FBI in a long-awaited interview Saturday over the use of her private email server, she said.

The purpose of the interview, which was voluntary, was to delve into whether Clinton mishandled classified information submitted on her private email system while she served as secretary of state. Her top staffers have already given testimony.

The interview happened at FBI headquarters in Washington, D.C., on the Saturday morning of the long holiday weekend, and lasted approximately three and a half hours, sources 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,” Clinton told NBC News’ Chuck Todd on Saturday.

Clinton said she stands by what she has been saying for a year — that she never sent or received emails marked classified at the time to her private account. She wouldn’t go into detail, citing the ongoing investigation.

Clinton's questioning marks what is believed to be the final step in the Justice Department's investigation.

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The FBI is looking into whether any laws were broken as a result of Clinton's use of a personal email server in her Chappaqua, New York, home. The issue has haunted her presidential campaign.

And the interview comes less than four weeks before the Democratic National Convention, where the party is expected to formally nominate Clinton as its candidate for the Nov. 8 election.

“I’m going to continue to put forth my record, what I have stood for and do everything I can to earn the trust of the voters of our country,” Clinton told Todd.

"You know when you've been in the eye of the tornado for as long as I have, I know there's a lot of incoming fire, I accept that. But I'm going to keep standing up and talking about what I have done and what I will do," she added.

Rumors that the FBI interview was to take place Saturday, first reported by The Daily Caller, emerged as the Clinton campaign was already mired in controversy over a chance meeting between Attorney General Loretta Lynch and former President Bill Clinton. The two met on Lynch's airplane on a tarmac in Phoenix on Monday, an unusual move for an attorney general during an ongoing investigation.

Lynch insisted their talk was purely "social" and said they didn't discuss the emails the Justice Department are currently reviewing. But she expressed regret Friday for the meeting.

"I certainly wouldn't do it again because I think it has cast a shadow over how this case will be perceived," Lynch said.

Lynch added that she won't recuse herself from the investigation and will look to the career prosecutors working on the case on whether or not to prosecute Clinton.

Clinton echoed Lynch on Saturday, calling the talk “a short chance meeting” and “an exchange of pleasantries.” She said she learned that her husband had spoken with Lynch “in the news.”

“Obviously no one wants to see any untoward conclusions drawn,” Clinton said. “They've said, you know, they would not do it again.”

Related: Lynch Won't Recuse Herself From Clinton Case

GOP lawmakers have called for an independent investigation into the emails, arguing the Justice Department may not be impartial in its review.

Presumptive GOP nominee Donald Trump, who was spending the weekend vetting potential running mates — including former House Speaker Newt Gingrich, New Jersey Gov. Chris Christie and Indiana Gov. Mike Pence — was incredulous over Bill Clinton's meeting with Lynch.

"He opened up a Pandora's box," Trump said earlier this week.

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

Neither Clinton nor Trump have public events scheduled for the Fourth of July weekend.