Special counsel Robert Mueller's team has been prodding ex-Trump campaign chairman Paul Manafort about his old consulting business partner, Roger Stone, according to a report.

Stone, a self-described political trickster and former confidant of the president, has reportedly piqued the interest of Mueller's office for appearing to foreshadow the WikiLeaks dump of John Podesta's emails when Podesta was Hillary Clinton's 2016 campaign chairman. The hack is believed to have been conducted by Russian intelligence officers under the pseudonym “Guccifer 2.0.”

Stone has denied colluding with Wikileaks and its founder Julian Assange to coordinate the release of damaging information on Clinton in order to boost President Trump's electoral prospects.

Manafort's cooperation, part of a plea deal reached in September to avoid a trial in Washington, comes as a number of Stone's associates have been questioned by Mueller's investigators. Others have appeared before the grand jury impaneled for the federal Russia probe. Stone has said he has not been contacted by prosecutors working for the special counsel.

Manafort and Stone were named partners of a consulting firm they founded in 1980 after meeting in the 1970s as young Republicans and working as aides for former President Richard Nixon's campaign.

Stone told ABC News, which first reported the story, that he was not surprised by Mueller's line of inquiry, especially considering he and Manafort “have been friends since childhood."

"I am highly confident Mr. Manafort is aware of no wrong doing on my part during the 2016 campaign, or at any other time, and therefore there is no wrongdoing to know about,” Stone told the outlet. “Narratives to the contrary by some in the media are false and defamatory."