(CNN) Audio of radio interviews between longtime Trump ally Roger Stone and the radio host he claimed was his back channel to WikiLeaks recently came into possession of special counsel Robert Mueller's office, two sources with knowledge of the matter tell CNN.

The interviews between Stone and comedian Randy Credico took place between August 2016 and April 2017 on Credico's radio show, which aired on local New York station WBAI. Stone has claimed that Credico served as his intermediary to WikiLeaks founder Julian Assange during the 2016 presidential election. Credico has denied the claim.

The special counsel's office is currently investigating Stone's possible involvement in Russian efforts to interfere in the 2016 election and questions about the nature of his supposed back channel to WikiLeaks.

CNN's KFile has obtained audio of the interviews, in which Stone and Credico repeatedly discuss WikiLeaks. In the interviews, you hear Credico ask Stone about the back channel and also cast doubt that the back channel exists.

While the interviews do not rule out the possibility Credico served as the back channel, the former radio host told CNN he believes the content of the interviews back up his denials.

"What you heard is what you heard because the radio doesn't lie," Credico told CNN.

Credico is a progressive activist in New York and outspoken supporter of Assange and WikiLeaks.

The news that the radio interviews are in the hands of the special counsel's office shows that Mueller's team still appears to be examining Stone's potential involvement with WikiLeaks, which released hacked emails from the Democratic National Committee and Hillary Clinton's campaign chairman during the 2016 presidential election.

The special counsel's office declined to comment.

Stone did not respond to repeated emails seeking comments and hung up when called by CNN's KFile team prior to publication. In an email sent two days after the story published, Stone said, "Your story is a false, misleading and inaccurate smear. A hatchet job."

Stone and Credico first discussed WikiLeaks publicly on August 23, 2016, where Credico asked Stone about his claims to be in touch with Assange.

"What about the October surprise? I mean, you've been in touch and indirectly with Julian Assange. Can you give us any kind of insight? Is there an October surprise happening?" Credico asked Stone.

"Well, first of all, I don't want to intimate in anyway that I control or have influence with the Assange because I do not," Stone said, adding he expects information to be released on the Clinton Foundation. "We have a mutual friend, somebody we both trust and therefore I am a recipient of pretty good information."

Assange appeared on Credico's program two days later on August 25. The host asked him about Stone's claim, and Assange denied he ever spoke with him.

"Roger Stone is a rather canny spinmaster and we have not had any communications with him whatsoever," Assange told Credico.

Credico at the time told local New York radio he did not believe Stone had a back channel

"I can tell you, Roger has no connection at all with them, other than the fact that he may say it off the top of his head," Credico said on September 30, 2016. "But you know him, he's a lot of braggadocio and this is an outrage that this guy would you -- because he could use it against me. I'm in London. I've had him on my radio show, am I an agent now?"

In March 2017, Stone again appeared on Credico's program. Stone had started to come under increased scrutiny for his comments suggesting a knowledge about the dates of WikiLeaks disclosure. In that interview, Credico again raises the topic of the "back channel." At no point is Credico mentioned as this conduit.

"You say you had a back channel to WikiLeaks," Credico asks Stone.

"I've been completely honest about this. I described it various ways on the record in a speech to a large number of Trump supporters," Stone says. "I described it as a back channel. I think in another interview I may have said intermediary. In the third interview I said a mutual friend. They are all true. They're all consistent and what I learned from this person, and don't blame me if I had better sources than the mainstream media was very simply this, that Assange had a substantial of information on Hillary Clinton and he would drop it in October."

Earlier in the same show, before speaking with Stone, Credico again said he did not know who the Stone back channel was. He questioned if Stone had a back channel at all.

"I don't know who the back channel is," Credico said. "I don't think there is a back channel."

In April, a month later, Stone again appeared on Credico's program. Stone was asked about the House Intelligence Committee's investigation. Stone denied knowing the details of the WikiLeaks content to be released, taking aim at Democratic House Intelligence Committee ranking member Adam Schiff, who had zeroed in on Stone's statements on WikiLeaks.

"He claimed that I knew in advance about the scope and timing and content of Wikileaks disclosures in October of last year," Stone said. "You know, WikiLeaks themselves, Randy, tweeted on July 31 of last year that they had enormous amount of material and Hillary Clinton and they would release it in October. So I'm not sure what the big state secret was here."

Update: This story has been updated with Stone's post-publication comment.