A classified email chain on Hillary Clinton’s personal server discussed an Afghan national’s ties to the CIA, a US government official has revealed.

A report that the Afghan national was on the CIA payroll was also in the chain, an official with knowledge of the document told Fox News.

The email exchange included then-Secretary of State Clinton, then-special envoy to Afghanistan and Pakistan Richard Holbrooke - who died in December 2010 - and possibly others.

A classified email chain on Hillary Clinton’s personal server discussed an Afghan national’s ties to the CIA and a report that the Afghan national was on the CIA payroll was also in the chain, a US official with knowledge of the document said

Democratic presidential candidate Hillary Clinton, left, responds on Wednesday to the crowd's applause after an introductory poem by Geneva Reed-Veal, the mother of Sandra Bland, who was found dead in a Texas jail cell

Clinton laughs during a campaign stop in Chicago on Wednesday, where she is joined by Geneva Reed-Veal, the mother of Sandra Bland, who was found dead in a Texas jail cell

It was one of 29 classified emails provided to congressional committees to be reviewed.

The emails about the foreign national reference a New York Times report, which, based on timing and details, Fox News claims to be one of two stories.

The first potential story is an October 2009 Times story about an Afghan national named Ahmed Wali Karzai, the half-brother of then-Afghan president Hamid Karzai, as a person who received “regular payments from the Central Intelligence Agency”

Or it could refer to an August 2010 Times story, which identified Karzai aide Mohammed Zia Salehi as being on the CIA payroll. Karzai was killed during a 2011 shootout.

It is unclear who initiated the discussion in the email exchange, or whether the Afghan national’s relationship with the CIA was confirmed.

A CIA spokesman said they had no comment on the email chain.

More than 550 that were released on Saturday, three of which were deemed to be 'secret', while another 84 were labelled classified.

One of the messages is a long note from David Satterfield, a top US diplomat to Egypt, who told White House and State Department officials about negotiations in the Sinai.

The message's contents have been deemed 'secret', though there is no sign they were labeled such at the time in which the email was sent, according to the Washington Times.

Mothers and sisters who have lost a family member to violence, stand behind Democratic presidential candidate Hillary Clinton during a campaign stop in Chicago on Wednesday

Clinton speaks at campaign stop at the Parkway Ballroom in Chicago on Wednesday. She met with family members of people struck down by gun violence during her visit

Clinton was forwarded the message by top aide Jacob Sullivan who asked Clinton to calm down the 'hysterical' US Ambassador to Pakistan, Cameron Munter, following the assassination of Osama bin Laden at a compound in Abottabad.

'Can you get me the facts (such as they are) before I talk with Kerry?' Clinton replied. The remainder of the email is highly redacted.

The department has now released more than 45,000 pages of emails from the private account Clinton used as secretary of state.

It plans to finish making her emails public on February 29, a day before the critical Super Tuesday primaries.

But ahead of the deadline previous deadline - January 29 - the State Department told the judge that they had discovered 4,000 additional emails that had not been checked for classified or private material.

The a top State Department open-records official took blame for not hitting the January deadline.

Clinton has struggled to put the email controversy to rest as she seeks the Democratic presidential nomination.

Last month, 22 emails were withheld in full because they contained 'top secret' material. The FBI also is examining the security of the homebrew server she maintained for email use while in office.