Former Secretary of State Hillary Clinton stored classified information sent from at least five different intelligence agencies on her private email system, including material relating to the 2012 Benghazi attacks, according to multiple media reports.

Clinton's system contained information from the National Security Agency, the Defense Intelligence Agency, the National-Geospatial Agency, the Office of the Director of National Intelligence and the Central Intelligence Agency, sources told Fox News.

The Office of the Intelligence Community Inspector General examined a random sampling of 40 of Clinton's emails and identified five that contained classified information. Clinton, the 2016 Democratic presidential front-runner, turned over a total of 30,000 emails to the State Department in December.

One of those emails determined to contain classified information was regarding Benghazi and was inadvertently released to the public by the State Department in May.

The intelligence community and State Department watchdogs have also warned that Clinton's home-brew email system potentially contains "hundreds" of classified emails.

Clinton has repeatedly said that she never sent or received classified information, but the numerous media reports over the past few months suggesting the contrary have put pressure on Clinton to turn over her private server for independent inspection. So far, Clinton has refused to do so.

McClatchy explains that as a result, Clinton has been "caught in a murky dispute between State Department and intelligence officials over whether emails on her server were classified."

The official responsible for overseeing the government's security classification system, John Fitzpatrick, told McClatchy that while reviewing four years of Clinton emails, intelligence agencies became concerned that State Department officials were not adequately protecting classified information while screening documents for public release.

The State Department commonly gathers and reports diplomatic information that "in an intelligence context could be read very differently," Fitzpatrick, the director of Information Security Oversight Office at the National Archives, told McClatchy.

"Even if Secretary Clinton or her aides didn't run afoul of any criminal provisions, the fact that classified information was identified within the emails is exactly why use of private emails . . . is not supposed to be allowed," said Bradley Moss, a Washington attorney who specializes in national security matters. "Both she and her team made a serious management mistake that no one should ever repeat."