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Fox News chief intelligence correspondent Catherine Herridge brought us some new information this morning on the FBI investigation of 22 top-secret emails from Hillary Clinton's private server.

The 22 emails have been deemed too damaging to national security to be released.

According to a source close to the investigation, a former Clinton staffer has disclosed how Clinton's unsecured personal email system was set up and who had access.

Bryan Pagliano, who set up the server in Clinton's home in 2009, was recently granted immunity by the Justice Department.

Herridge reported that investigators are now getting "a kind of roadmap" from Pagliano and "his importance to the FBI case cannot be overemphasized."

His testimony is said to be helping investigators "knit together the emails with other evidence," Herridge said.

Clinton recently said she was "delighted" that Pagliano is cooperating "as everyone else has."

Herridge noted that other emails from the server contain information from foreign government sources that is "born classified."

Clinton has maintained she never sent or received any emails on the server that were "marked classified." She has said the emails were later deemed to contain classified information.

Herridge noted that federal rules stipulate that classified material is based on "the content, not its markings."

Watch Catherine's full report above.

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