US Special Counsel Robert Mueller disclosed for the first time on Friday that his office has evidence of communications between Roger Stone, a longtime advisor to President Donald Trump, and WikiLeaks related to the release of hacked Democratic Party emails, according to CNBC.

In a court filing on Friday, Mueller’s office said it had gathered that evidence in a separate probe into Russian intelligence officers who were charged by Mueller of hacking the emails during the 2016 US presidential campaign and staging their release.

Stone was indicted last month for lying to Congress about his communications with others about the hacked emails. Stone, an ally of Trump for 40 years, has pleaded not guilty to the charges.

Stone has previously acknowledged brief exchanges with both WikiLeaks and Guccifer 2.0, a hacker persona US intelligence agencies say was a cover name used by Russian military intelligence, but maintains he never had advance knowledge about the release of hacked emails.