(CNN) An investigation by the State Department released on Friday said there was no "persuasive evidence" of widespread mishandling of classified information in the controversy surrounding Hillary Clinton's use of a private email server while she was secretary of state.

An unclassified report detailing the investigation was sent to Sen. Chuck Grassley, an Iowa Republican and a member of the Senate Judiciary Committee, and he released it publicly Friday afternoon. The Associated Press was first to report on the findings.

The report states that 38 people employed at one time by the State Department had sent classified emails to Hillary Clinton's private email server and there were nearly 100 violations of classification rules. Still, "by and large, the individuals interviewed were aware of security policies and did their best to implement them in their operations."

"There was no persuasive evidence of systemic, deliberate mishandling of classified information," the report states.

The report is yet another instance of federal investigators clearing Clinton and her aides of deliberately mishandling classified information, which was the focus of attacks on the former secretary of state throughout the 2016 presidential campaign. Clinton was also cleared of wrongdoing by the FBI twice over her private email server during the campaign.

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