Democratic presidential candidate Hillary Clinton picks out fresh corn during a visit to Dimond Hill Farm in Hopkinton, New Hampshire July 28, 2015. REUTERS/Brian Snyder

Classified emails that were stored on the private email server of former Secretary of State Hillary Clinton contained information from five US intelligence agencies, McClatchy reports.

A congressional official with knowledge of the matter told McClatchy that intelligence officials who saw the five classified emails determined that they included information from five US spy agencies.

One classified email — now public and pertaining to the 2012 terrorist attack in Benghazi — reportedly contained information from the National Security Agency, the Defense Intelligence Agency (DIA), and the National Geospatial-Intelligence Agency.

McClatchy added, citing the official, that the "other four classified emails contained information from the Office of the Director of National Intelligence [DNI] and the CIA."

Last week, government inspectors told the Justice Department in a letter that "secret government information may have been compromised in the unsecured system she used at her New York home during her tenure as secretary of state," according to The Associated Press.

The inspectors requested the department to look into the possible mishandling of classified information on the server from Clinton's tenure as secretary of state.

Clinton, Democratic presidential front-runner in the 2016 election, has repeatedly said she broke no laws or rules by forgoing a standard government email account in favor of the private account. She has also said, as recently as last weekend, that she is "confident" she did not send or receive classified information by email.

Clinton spokesman Nick Merrill said in a statement last week that Clinton "followed appropriate practices in dealing with classified materials."

Democratic U.S. presidential candidate Hillary Clinton speaks at an organizing event at the Iowa State University Alumni Center in Ames Thomson Reuters

But the inspector general of the intelligence community, in a letter to Congress, said a limited sampling of Clinton's emails in question found at least four that contained classified information and should have been considered secret.

If Clinton had a technical security team to monitor her server for suspicious activity, Clinton could have had a system at least as secure at the State Department. If not, the information would have been vulnerable.

“The layers of security that would have to be employed to make a privately run exchange server as secure as something that is secured by the federal government would be pretty significant,” Timothy Ryan, a former FBI supervisory special agent who now manages cyber investigations for Kroll, told The Washington Post in March. “It’s not that it can’t be done. I just find it improbable."

Clinton has said that the email system was established during Bill Clinton's presidential administration (1993-2001), and her team has stated that "her family’s electronic communications was taken seriously from the onset."

Hillary Clinton talks with students working on computers during her time as first lady. REUTERS

No matter the level of security the Clintons employed — which is still largely unknown — the fact that this information was found on her personal server highlights why officials in her position are supposed to use government emails.

“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, told McClatchy. “Both she and her team made a serious management mistake that no one should ever repeat.”

Broader questions about Clinton's private email server have at times drawn attention away from the Democratic front-runner's presidential campaign. The latest disclosure comes the same day as the release of a poll showing that a majority of voters nationwide do not consider her "honest and trustworthy."

A separate poll released last week showed that she also trailed three strong Republican contenders — former Florida Gov. Jeb Bush of Florida, Wisconsin Gov. Scott Walker, and US Sen. Marco Rubio of Florida — in theoretical general-election matchups in the key swing states of Colorado, Iowa, and Virginia.