Former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonBloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close Trump pledges to make Juneteenth a federal holiday, designate KKK a terrorist group in pitch to Black voters MORE trolled President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE on Monday over a report that the State Department has intensified a probe into her private email server while House Democrats open an official impeachment inquiry into Trump.

News regarding the email investigation, which comes years after the Department of Justice wrapped up its own probe into the "homebrew" server, prompted a swift rebuke from Sen. Kamala Harris Kamala HarrisTexas Democratic official urges Biden to visit state: 'I thought he had his own plane' The Hill's Campaign Report: Biden on Trump: 'He'll leave' l GOP laywers brush off Trump's election remarks l Obama's endorsements A game theorist's advice to President Trump on filling the Supreme Court seat MORE (D-Calif.), who praised Clinton, the 2016 Democratic presidential nominee, as someone who "served our country with distinction and always put our country first — something Trump knows nothing about."

"But my emails," Clinton responded, echoing a line Democrats have often used mockingly when Trump has faced negative headlines throughout his term.

But my emails. (Thank you.) — Hillary Clinton (@HillaryClinton) September 30, 2019

The Washington Post on Sunday reported on the Trump administration's renewed efforts to investigate Clinton's use of a private email server while serving as the nation's top diplomat.

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According to the Post, the State Department has contacted as many as 130 former Clinton aides in recent weeks as part of a probe into the email records of officials who sent messages to Clinton during her time as secretary of state.

Many of the aides have reportedly been informed that their emails have been retroactively classified and that the messages may amount to security violations as a result.

Officials told to the Post that investigators within the State Department began looking into the matter about 18 months ago. The department appeared to then drop the effort, before reviving it again in August, the Post said.

The State Department did not immediately respond to a request for comment from The Hill.

The State Department, FBI and Congress had all opened earlier investigations into Clinton's use of a private email server during her time as secretary of State. The FBI said in 2016 that its review of her private server found no evidence of criminal wrongdoing, though described her use of it as "careless."

Clinton is among those who have called for Trump's impeachment following a recent whistleblower's complaint that alleges he sought to pressure a foreign ally into investigating a potential 2020 presidential rival.

Trump has denied any wrongdoing, but a partial transcript of the call in question released last week by the White House has only inflamed Democrats further.