Washington (CNN) Special counsel Robert Mueller's scrutiny of Roger Stone includes investigating whether Stone had backchannels to WikiLeaks during the 2016 election beyond the New York radio host and political activist whom Stone claims was his primary go-between, according to people familiar with the matter.

Investigators' queries to people connected to Stone, a longtime ally of President Donald Trump, suggest Mueller's team is skeptical of Stone's explanation that Randy Credico was his main intermediary, according to people familiar with interviews conducted by investigators. The scrutiny also includes probing Stone's relationship with right-wing journalist and conspiracy theorist Jerome Corsi about whether he also acted as a go-between with Stone and WikiLeaks founder Julian Assange, a source said.

Additionally, investigators are looking into whether Stone shared information that he believed was from WikiLeaks with members of Trump's presidential campaign, according to a source familiar with the probe. Investigators have been provided recordings of Stone claiming he talked to Trump regularly early in the 2016 presidential campaign, CNN has learned. Later, after various document dumps from WikiLeaks, Stone claimed in separate communications he should receive credit for coordinating with the group, the source said.

The queries about whether Stone may have shared information with the Trump campaign are a strong indication that Mueller's team is still actively investigating the possibility that someone close to Trump engaged in collusion with the Russians.

"We have said over and over again that he shared nothing with the campaign because he had nothing to share," said Grant Smith, an attorney for Stone. "He received nothing from anybody. At what point does this old record get worn out from being played over and over again?"

"I never discussed WikiLeaks stuff with Trump and would never have said I should get credit for coordinating with WikiLeaks since I did no such thing," Stone said.

A spokesman for the special counsel declined to comment. A lawyer for the President declined to comment.

In an interview with the Associated Press last year, Trump denied that he knew about WikiLeaks before the shadowy website started releasing hacked Democratic emails during the 2016 presidential campaign.

The President said, "When WikiLeaks came out ... never heard of WikiLeaks, never heard of it. When WikiLeaks came out, all I was just saying is, 'Well, look at all this information here, this is pretty good stuff.'"

Stone's associates questioned on contacts

While Stone said he has not been contacted by Mueller's team, many of his associates have been called in for interviews or testimony before the grand jury. Witnesses said the main focus of their interviews has been Stone's contact with WikiLeaks and Assange. Some of them are still actively cooperating with Mueller's team and have handed over troves of communications involving Stone, according to sources familiar with the matter.

A key area of inquiry is whether Stone actually received information from WikiLeaks and who helped facilitate that information-sharing. Investigators' questions to Corsi about his communications with WikiLeaks and Stone indicate they are trying to determine whether Stone had other go-betweens with WikiLeaks.

Corsi has participated in hours of interviews with Mueller's team and testified before the grand jury, according to sources familiar with the situation. Corsi's lawyer declined to comment.

At one point, Corsi appeared to provide cover for one of Stone's most inflammatory tweets: His summer 2016 claim that "it will soon (be) the Podesta's time in the barrel." It was later seen as an indication Stone may have had advance warning that then-Clinton campaign chairman John Podesta's hacked emails would soon be public.

In March 2017, Corsi -- who was then the Washington bureau chief for InfoWars -- wrote, "Having reviewed my records, I am now confident that I am the source behind Stone's tweet." In his article , Corsi claimed his own research inspired Stone's Twitter missive. Stone has since said he was referring to the business dealings of both John Podesta and his brother, DC lobbyist Tony Podesta.

Stone has suggested that the special counsel may be interested in Corsi's own relationship with Trump rather than Corsi's interactions with Stone. But a person familiar with the situation said investigators were mainly interested in Corsi's interactions with Stone and whether he acted as Stone's backchannel.

Stone told CNN, "Corsi told me he was never in communication with WikiLeaks or Assange, I believe him and know of no evidence to the contrary."

Corsi's own attorney denied to CNN back in September that his client was in touch with Assange, WikiLeaks or Guciffer 2.0, US intelligence has determined that the online persona Guccifer 2.0 was a front for Russian intelligence and Russian officers who hacked Democrats and passed the stolen material on to WikiLeaks during the campaign.

Stone's own words fuel questions

Stone has been under scrutiny for his contact with Guccifer 2.0 and comments he made in 2016 that appeared to suggest he had advance knowledge of material from WikiLeaks before it was released.

"I actually have communicated with Assange," Stone said in a speech in Florida on August 8, 2016. "I believe the next tranche of his documents pertain to the Clinton Foundation but there's no telling what the October surprise may be."

The Atlantic reported Stone and WikiLeaks exchanged direct messages on Twitter, but both have denied that they were in direct contact about the release of Clinton emails.

Stone told CNN that "although my claims were dramatized for effect before a partisan audience, they were not fabricated and I clarified in a dozen interviews that my 'communication' with Assange had been through a third party." He added, "I had no advance knowledge of the source or content of the material WikiLeaks would ultimately release."

Meanwhile, Stone's claim that he used Credico as that third party has been met with inconsistencies as well as denials from Credico. The radio host, who is open about his friendship with Assange, has denied funneling information back-and-forth to Assange on Stone's behalf.

"I am a decoy, the patsy to divert attention," Credico told CNN. "Or he just didn't have one (an intermediary) and his ego was too big to admit that."

Stone also suggested to reporters and associates that he had other links to WikiLeaks. A source familiar with the matter said Credico told the grand jury that Stone mentioned having another link to WikiLeaks.

"I did tell Credico I had an additional source who also told me the material was coming and that the revelations would address the Clinton Foundation," Stone told CNN.

When he appeared before the House Intelligence Committee last year, Stone testified that he had no direct contact with Assange during the election and instead relied on a go-between.

In a letter following his committee appearance, Stone's lawyer identified his intermediary as Credico.

"Mr. Stone noticed Credico had traveled to London on at least two occasions and conducted two landmark interviews with Julian Assange on WBAI," Stone's lawyer wrote, referring to the New York progressive radio station where Credico worked.

But Stone's timeline doesn't align with public events.

Stone claims that Credico's interviews with Assange inspired Stone to use Credico as a backchannel, according to the letter from Stone's attorney. But Credico didn't interview Assange until August 25, 2016, weeks after Stone started touting an intermediary. Stone now says that he knew Credico had ties to WikiLeaks even before the Assange interview.

As first reported by CNN , in multiple radio interviews between Credico and Stone -- now in the special counsel's possession -- Credico also asked Stone about the backchannel and expressed doubt that any such backchannel exists.

In yet another discrepancy, the letter from Stone's lawyer to the House committee also insists that Stone had only ever asked Credico to confirm information that Assange had shared publicly in media interviews or via social media.

But on September 18, 2016, Stone asked Credico to ferret out other information from Assange that Stone believed would be damaging to Hillary Clinton. "Please ask Assange for any State or HRC e-mail from August 10 to August 30...," a portion of the email from Stone to Credico says about Clinton emails from 2011.

"My testimony before the House Intelligence Committee was entirely truthful and there is no credible evidence to the contrary," Stone told CNN, maintaining that Credico was his primary backchannel and that he has associates who will corroborate his account.

"From the beginning, I wanted to protect the identity of Credico, because I knew that his support for Julian Assange and the journalistic independence of WikiLeaks would not be popular in the progressive left circles where he made a living," Stone said. "I turned over Randy Credico's name to the House Intelligence Committee only reluctantly."

Stone's lawyer said there were "no inconsistencies in what we sent to the House."

While Stone has proclaimed his innocence, he has said he believes Mueller's team could bring charges against him to try to force him to cooperate against Trump.

Prosecutors may also be confronted with the possibility that Stone, a braggadocios self-proclaimed "dirty trickster," did not actually have access to a legitimate backchannel providing him information from WikiLeaks.

"He may have had somebody, I don't know," said Credico. "Who can tell with this guy?"

UPDATE: This story has been updated to add more detail about previous reporting from the Washington Post and Wall Street Journal.

CORRECTION: This story has been corrected to reflect when Trump did his interview with the Associated Press.