Washington (CNN) President Donald Trump's administration is investigating the emails of dozens of current and former senior State Department officials who sent emails to then-Secretary of State Hillary Clinton's private email, The Washington Post reported Saturday.

Current and former officials tell the Post that as many as 130 officials have been contacted in recent weeks by investigators at the State Department. Those targeted, including senior officials as well as others in lower-level jobs, have been notified that emails they sent years ago have been retroactively classified and now are potential security violations, according to letters reviewed by the Washington Post.

Current officials, as well as former Obama administration officials, told the Post that the uptick in the investigation was an extraordinary crackdown by a Trump administration that has left the security of its own information vulnerable to foreign surveillance.

CNN has reached out to Hillary Clinton's camp for comment.

The report of the intensifying email probe against Trump's 2016 political rival comes days after the release of a whistleblower complaint that alleges Trump abused his official powers "to solicit interference" from Ukraine in the upcoming 2020 election, and that the White House took steps to cover it up. Trump has denied any wrongdoing. A transcript released by the White House shows Trump repeatedly pushed Ukrainian President Volodymyr Zelensky to investigate former Vice President Joe Biden, his potential 2020 political rival, and his son, Hunter Biden.

Read More