Brian J. Tumulty

USA TODAY

The FBI interviewed Hillary Clinton on Saturday morning as part of the investigation into her use of a private email server for official emails while she served as secretary of State, campaign spokesman Nick Merrill said.

"She is pleased to have had the opportunity to assist the Department of Justice in bringing this review to a conclusion,'' Merrill said in a statement, describing the meeting as voluntary. "Out of respect for the investigative process, she will not comment further on her interview.''

Clinton, who left office as secretary of State in February 2013 and is now the presumptive nominee on the Democratic ticket for president, used a private email and server hosted at her home in New York — inconsistent with long-established policies governing all federal agencies.

FBI agents interviewed Hillary Clinton, now what?

In an interview with NBC's Chuck Todd for Meet the Press on Saturday, Clinton said she was eager to help investigators conclude their review.

"I never received nor sent any material marked classified," Clinton said, adding later that she has had the same answers since last summer about the emails and has released a trove of some 55,000 messages.

Clinton has said the system was “absolutely permitted” and commonplace for private communications. But an independent State Department inspector general report in May said the use was not appropriate largely because it didn’t comply the Federal Records Act and was vulnerable to hackers.

The 3½-hour interview Saturday was conducted at FBI headquarters in downtown Washington, according to a Clinton aide. The meeting had been anticipated as the FBI investigates whether classified information was compromised by her email arrangement. The agency must now decide on an official recommendation on a formal indictment.

Republican National Committee Chairman Reince Priebus described the questioning of Clinton as unprecedented for a major party presidential candidate. "That the FBI wanted her for questioning reinforces her central role in deliberately creating a culture which put her own political ambitions above State Department rules and jeopardized our national security,'' Priebus said.

The meeting steers the probe to an expected conclusion in the coming weeks, perhaps ahead of the Republican and Democratic national conventions, which start the week of July 18.

On Friday, Attorney General Loretta Lynch pledged to accept the decision of career prosecutors, investigators and FBI Director James Comey on whether to bring criminal charges in the investigation. Her comments came after she faced a storm of criticism related to an awkward encounter with former president Bill Clinton earlier this week.

"This case will be resolved by the team that has been working on it from the beginning,'' Lynch said, acknowledging that the meeting with Bill Clinton "cast a shadow'' over the ongoing inquiry.

AG Lynch will accept decision of FBI, prosecutors on Clinton email probe

In her phone call with NBC on Saturday, Clinton said she first heard of the encounter from news reports.

"It was a short, chance meeting on an airport tarmac," Clinton said. "They said hello, they talked about grandkids, which is very much on our minds these days, golf, their mutual friend former Attorney General Janet Reno ... it was purely social, they did not veer from speaking about those very common exchanges."

If the FBI director and the Justice Department prosecutors disagree on whether to prosecute, Lynch may have to delegate that tie-breaking decision to a deputy, said professor Carl Tobias of the University of Richmond School of Law.

The State Department's Office of Inspector General in May found the former secretary of State disregarded cybersecurity guidelines by using a private email server during her tenure, and that she did not seek authorization for her email account.

The audit also found Clinton and her predecessors as secretary of State poorly managed computer systems. By the time Clinton took over as secretary of State in 2009, the standards for email security were "considerably more detailed and more sophisticated" than for previous secretaries of State.

State Dept. audit hits Clinton over email use

The department revised guidelines through 2011, according to the report, and "Secretary Clinton's cybersecurity practices accordingly must be evaluated in light of these more comprehensive directives."

Nevertheless, the recommendations in the report were limited to forward-looking measures to better inform employees of department policies and for improving cybersecurity.

Six key excerpts from the State Dept. report on Clinton's emails