Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE received just one formal briefing about how to handle classified materials during her four years as the secretary of State, according to internal documents released to the Daily Caller.

The lone security briefing came on Jan. 22, 2009, just a day after Clinton was confirmed by the Senate to serve as the nation’s top diplomat, records released to the news organization under a Freedom of Information Act request show.

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The single briefing appears to violate a portion of the department’s Foreign Affairs Manual, which declares that senior staffers receive training on “identifying and marking” classified material “on an annual basis.”

The lack of documentation does not preclude the possibility that Clinton received informal briefings and updates about government classification processes or that her subsequent briefings were not memorialized in writing.

But it is likely to further inflame ire from the Democratic presidential front-runner's critics, who have repeatedly alleged that her private email server jeopardized American security. Of the roughly 30,000 emails released by the State Department from Clinton’s server, about 2,000 were classified at some level. Another 22 emails were deemed “top secret” — the highest level of classification — and deemed too sensitive to release even in a heavily redacted form.

On Thursday, State Department spokesman Mark Toner said that “everybody in this building” receives “that type of training and awareness.”

“We all have to undergo that, and it’s considered mandatory,” he said, without referring to Clinton’s case in particular.