The Trump administration has revived an investigation into email records from Hillary Clinton's former aides, The Washington Post reported Saturday.

Investigators reportedly reached out to roughly 130 officials in recent weeks over years-old emails, and told them the emails were retroactively classified and are now considered potential security violations.

The investigation began roughly 18 months ago, but the officials told The Post that investigators appeared to drop the effort but picked it up again last month.

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State Department investigators in recent weeks have been contacting former Hillary Clinton aides over their email records, The Washington Post reported Saturday evening.

Investigators have reached out to roughly 130 officials in recent weeks over years-old emails and told them the emails were retroactively classified and are now considered potential security violations, The Post reported, citing current and former State Department officials and letters they received.

The officials received letters in August saying, "You have been identified as possibly bearing some culpability" in "security incidents," according to The Post.

The investigation began roughly 18 months ago, but the officials told The Post that investigators appeared to drop the effort but picked it up again last month.

The Post cited two senior State Department official who said the probe was not politically motivated, and one said that it took roughly three-and-a-half years to go through "millions of emails."

US President Donald Trump delivers remarks at the Hispanic Heritage Month Reception at the White House in Washington, DC, September 27, 2019. Jim Watson/AFP/Getty Images

The timing of the revived investigation is already being scrutinized — President Donald Trump has recently become the subject of House Democrats' impeachment inquiry after revelations that he pressed the Ukrainian president to investigate one of his top political rivals.

The Post cited one former senior US official familiar with the State Department's investigation who said the renewed push targeting former Clinton aides was a way for Republicans to "keep the Clinton email issue alive" and "tarnish a whole bunch of Democratic foreign policy people."

Read more: Hillary Clinton isn't running for president, but Trump is still running against her

Clinton's use of a private email server when she was Secretary of State unleashed a years-long controversy that rattled her 2016 presidential bid and fueled calls from Trump and many Republicans for criminal prosecution.

Clinton was previously investigated by the State Department, as well as the FBI and Congress. Though former FBI Director James Comey infamously accused Clinton of being "extremely careless" in her handling of classified information, she was never criminally charged.