The White House has launched a probe of the use of private email accounts by senior aides, Politico reported Thursday, citing four unnamed officials familiar with the matter.

The probe comes on the heels of a Politico investigation that found that several current and former senior White House staff — including Jared Kushner, Ivanka Trump, Gary Cohn, Steve Bannon and Reince Priebus — used private email accounts.

It is illegal to conduct official business on a non-government email account without preserving the emails for record keeping.

President Donald Trump turned Hillary Clinton’s use of a private email server as secretary of state into a key attack against her, leading chants of “lock her up” and promising to prosecute Clinton once in office (he went back on that promise after the election).

One of Politico’s unnamed sources said the White House counsel’s office was reviewing the private accounts in order to determine if any messages were relevant to the congressional or special counsel investigations of Russian meddling in the 2016 election.

CNN reported Thursday night that Kushner did not share the existence of his private email account with Senate Intelligence Committee staffers in a private interview, reportedly angering the committee chair and vice chair.

“The Committee was concerned to learn of this additional email account from the news media, rather than from you, in your closed staff interview,” Chairman Richard Burr (R-NC) and Vice Chairman Mark Warner (D-VA) wrote in a letter to Kushner published by CNN.