"Top secret" material was sent through Hillary Clinton's private email server during her tenure as secretary of state, according to the U.S State Department.
At least 22 emails sent through Hillary Clinton's private server contain some of the government's most sensitive secrets, a State Department official confirmed on Friday night.
As a result, the 22 messages will be withheld from the public due to their sensitive nature, and have been classified as "top secret," State Department spokesman John Kirby said on Friday.
"The documents are being upgraded at the request of the intelligence community because they contain a category of top secret information," Kirby stated.
The announcement takes place three days ahead of the Iowa caucuses, when the first votes are cast for the presidential nominations and where Clinton is locked in a tight race with Vermont Senator Bernie Sanders to become the Democratic nominee for the Nov. 8 U.S. presidential elections.
Clinton, who is seeking the Democratic nomination for the 2016 election, has been under fire for using a private computer server for work emails while in office.
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The government has been investigating the former secretary of State's private email server since last July, when the inspector general for the intelligence community issued a security referral warning that classified information could have been mishandled.
Thousands of those emails have been released by the State Department, but this is the first time her messages have been labelled classified at any level.
The government forbids handling of classified information, which may or may not be marked that way, outside secure government-controlled channels, and sometimes prosecutes people who remove it from such channels.
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