Presumptive Republican nominee Donald Trump called for charges to be filed against Democratic candidate Hillary Clinton Saturday after the former secretary of state met with the FBI regarding the agency’s investigation into her use of a private email server for official correspondence.

"It is impossible for the FBI not to recommend criminal charges against Hillary Clinton," Trump tweeted Saturday afternoon. "What she did was wrong! What Bill did was stupid!"

The Clinton campaign said the voluntary meeting lasted about three-and-a-half hours and took place at FBI headquarters in Washington.

Clinton “is pleased to have had the opportunity to assist the Department of Justice in bringing this review to a conclusion” campaign spokesman Nick Merrill said in a statement. He also said Clinton, the presumptive Democratic presidential nominee, would have no further comment about the interview.

The campaign issued the statement Saturday shortly before 12:30 p.m. ET, practically minutes after Clinton returned to her Washington home, then departed again about 30 minutes later.

“Hillary Clinton has just taken the unprecedented step of becoming the first major party presidential candidate to be interviewed by the FBI as part of a criminal investigation surrounding her reckless conduct,” said Republican National Committee Chairman Reince Priebus. "We must ask ourselves if this is the kind of leadership we want in the White House.”

There was no immediate comment from the FBI or Justice Department Saturday. 

Clinton’s use of a private server and email address -- and whether classified information was mishandled as a result of that setup -- has cast a shadow over her campaign from the start.

The FBI investigation is purportedly coming to a close, and the Clinton interview is considered among the final steps in the case.

Trump has seized on the email issue and repeatedly said the probe undermines Clinton's fitness for office. Trump has called his opponent "Crooked Hillary" and said she cannot be trusted in the White House.

The former first lady and New York senator has argued that she is more trustworthy than Trump on handling the issues that matter to most Americans: foreign policy, national security and running the economy.

But the email investigation has lingered throughout her campaign, and Trump has asserted that Clinton will receive leniency from a Democratic administration.

Earlier this week, the entire, ongoing email scandal grew when Clinton’s husband, former President Bill Clinton, initiated an impromptu meeting with Attorney General Loretta Lynch on her airplane in Phoenix.

"The American people need to have confidence that the Obama Justice Department is conducting a fair and impartial investigation, but when the attorney general meets secretly with Bill Clinton just days before Hillary’s interrogation is conducted discreetly over a holiday weekend, it raises serious concerns about specialtreatment,” Priebus also said.

There was already speculation about whether an agency under the Obama administration could conduct an unbiased probe, which only intensified after Clinton met with Lynch, a President Obama appointee who decides whether to bring charges in the case.  

Lynch says she will accept whatever recommendations she receives from the agency's career prosecutors and lawyers.

Clinton has said relying on a private server was a mistake but that other secretaries of state had also used a personal email address. The matter was referred for investigation last July by the inspectors general for the State Department and intelligence community following the discovery of emails that they said contained classified information.

The State Department's inspector general, the agency's internal watchdog, said in a blistering audit in May that Clinton and her team ignored clear warnings from State Department officials that her email setup violated federal standards and could leave sensitive material vulnerable to hackers. Clinton declined to talk to the inspector general, but the audit reported that Clinton feared "the personal being accessible" if she used a government email account.

Agents have already interviewed top Clinton aides including her former State Department chief of staff Cheryl Mills and Huma Abedin, a longtime aide who is currently the vice chairwoman of Clinton's campaign.

The staffer who set up the server, Bryan Pagliano, was granted limited immunity from prosecution by the Justice Department last fall in exchange for his cooperation. The FBI as a matter of course seeks to interview individuals central to an investigation before concluding its work.

The emails were routed through a server located in the basement of Clinton's New York home during her tenure as the nation's top diplomat from 2009 to 2013.

Dozens of the emails sent or received by Clinton through her private server were later determined to contain classified material.

Clinton has repeatedly said that none of the emails were marked classified at the time they were sent or received. As part of the probe, she has turned over the hard drive from her email server to the FBI.

The Associated Press contributed to this report.