Former Trump campaign chairman Stephen K. Bannon was interviewed by the special counsel on Friday, the Washington Post reports.

Specifically, the perpetually disheveled former Breitbart editor was reportedly questioned about alleged claims that Roger Stone made regarding foreknowledge of Wikileaks’ release of Clinton emails hacked by Russian government agents.

Prosecutors are interested in potential coordination between the Trump campaign, Stone, and Wikileaks in when and how to release the hacked messages.

The development comes amid reports that Special Counsel Robert Mueller’s investigation into Stone is accelerating. The Wall Street Journal reported today that investigators have homed in on a series of conference calls Stone made in August 2016 in which he told callers that Wikileaks was planning to release hacked emails from the Clinton campaign.

Stone associates Randy Credico and Jerome Corsi have been interviewed over the past six weeks, as well.

NBC reported that Florida attorney Bruce Rogow is now leading Stone’s defense in the Mueller investigation.

Bill Burck, an attorney for Bannon, did not immediately return a request for comment.

“Mueller’s team has been very professional and courteous. Out of respect for the process, I will not discuss my interviews with them, but people shouldn’t believe everything they read,” Bannon told the Washington Post in a statement.