Special counsel Robert Mueller’s team has been asking its latest cooperating witness, Paul Manafort, about former Trump associate Roger Stone, ABC News reported.

According to multiple sources familiar with the matter who spoke to ABC News, Mueller’s interests in Stone are tied to his contacts with WikiLeaks founder Julian Assange and his leak of Hillary Clinton’s campaign emails.

Manafort and Stone have been longtime friends and former business partners. It’s unclear if Manafort has shared any information about Stone with Mueller’s team, but Stone told ABC he’s “confident” 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.”

“Narratives to the contrary by some in the media are false and defamatory,” Stone said.