The State Department reportedly has ramped up its investigation into Hillary Clinton’s private server, potentially reviving an issue that dominated the 2016 presidential election campaign.

The Washington Post, citing current and former U.S. officials, reported late Saturday that as many as 130 current and former officials whose emails found their way into Clinton's inbox have been contacted by investigators. According to The Post, those officials have received letters notifying them that their emails from years ago have been retroactively classified and their transmission could constitute security violations.

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State Department investigators began contacting the officials around a year and a half ago, then the investigation seemed to fall by the wayside before picking up steam again last month, officials said.

Senior State Department officials denied they were acting at the specific direction of President Trump, who is facing an impeachment inquiry led by House Democrats.

“The process is set up in a manner to completely avoid any appearance of political bias,” a senior State Department official told The Post.

“This has nothing to do with who is in the White House,” said a second senior State Department official.“This is about the time it took to go through millions of emails ...”

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Several of those questioned, however, told the Post that investigators seemed to be pursuing the matter "reluctantly, and under external pressure."

Jeffrey Feltman, a former assistant secretary for Near East Affairs, told the paper he found the recent retroactive classification of more than 50 of his emails to be out of the ordinary. “I’d like to think that this is just routine, but something strange is going on.”

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Those being investigated will not face criminal prosecution since the FBI investigation of the Clinton email case closed before the 2016 election.

The FBI began investigating Clinton's use of a private email server in July 2015 based on a referral from the intelligence community inspector general. In July 2016, then-FBI director James Comey announced he was recommending the case be closed with no charges, saying Clinton and her aides' handling of classified information was "extremely careless" but not criminal.

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