Washington (CNN) Special counsel Robert Mueller sought information directly last year from one of Donald Trump's campaign pollsters who is also a former business associate of Paul Manafort's.

Mueller's team met with pollster Tony Fabrizio in February 2018, an interview that has not been previously reported and takes on new significance after Manafort's attorneys revealed Tuesday that Mueller's team is still interested in how Manafort shared polling data with his Russian intelligence-linked colleague.

CNN journalists observed Fabrizio leaving the special counsel's office on the first of February last year and have since confirmed he was meeting with Mueller's team. At the time, the special counsel had been digging into Manafort's finances and political work ahead of his trial.

In a filing Tuesday, Manafort's attorneys tried to redact the fact that prosecutors knew Manafort shared polling data related to the 2016 presidential election with his Russian intelligence-linked associate Konstantin Kilimnik while Manafort was running Trump's presidential campaign. The information was supposed to remain secret because it's part of an ongoing investigation, but it was revealed because of a formatting error in the filing.

Fabrizio's involvement with Mueller is intriguing because he's one of the few people in Manafort's orbit with knowledge of the inner-workings of the Trump campaign as well as Manafort's Eastern European connections.

A veteran pollster and political strategist, Fabrizio worked on Ukrainian elections with Manafort and went on to serve as the Trump campaign's chief pollster beginning in the spring of 2016.

A source familiar with the special counsel's interest said Fabrizio's interview included questions about his polling work for Manafort in Ukraine rather than his internal Trump campaign polling. It is not clear what other topics were broached in the interview or whether it solely focused on Fabrizio's knowledge of Manafort's business dealings.

The Justice Department initially asked Mueller to look into Manafort's political ties in Ukraine because they may relate to other allegations of Russian coordination with the Trump campaign.

Fabrizio would not comment for this story.

When asked Thursday if he had any knowledge that Manafort shared polling data with a Russian, President Trump said, "No. I didn't know anything about it. Nothing about it."

More than a dozen people affiliated with the Trump campaign have been interviewed by the Mueller team, according to the President's legal team

Trump's first pollster

For much of the 2016 race, Trump had been famously averse to hiring pollsters. He insisted they were a waste of money and that his gut was more valuable than any poll he could commission.

But when Manafort was hired, the newly minted campaign chairman aimed to professionalize the political apparatus. As part of that effort, he recruited Fabrizio, who already had close ties to Manafort and other Trump allies, including Trump's longtime political adviser Roger Stone. But he never forged particularly close ties with the candidate, despite having done some prior work for Trump's businesses.

His relationship with Trump soured late in the election as the Trump campaign disputed a bill of roughly $767,000 to Fabrizio's polling firm. Fabrizio's firm was eventually compensated.

The source familiar with the situation said Fabrizio was unaware of who Manafort and his deputy, Rick Gates, had shared campaign data with during the election.

The revelation about the exchange of poll data between Manafort and Kilimnik sparked alarm among Democrats this week and fueled speculation that the Russians could have used such information to tailor their efforts to meddle in the 2016 election.

"This appears as the closest we've seen yet to real live actual collusion," Virginia Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, told CNN Wednesday. "Did the Russians end up using this information in their efforts that took place later in the fall where they tried using the Internet Research Agency and other bots and other automated tools on social media to suppress, for example, the African-American vote? Was that something that was driven by this campaign data that was turned over to the Russians?"

Manafort's consulting world

Fabrizio had long been among Manafort's circle of political operatives and became part of the cast of characters mentioned during his criminal trial last summer.

At trial, Mueller's team painted a picture of a well-oiled Ukrainian lobbying operation in which Manafort and his colleagues took in millions of dollars a year from pro-Russian oligarchs, some of which was funneled through secret, illegal offshore bank accounts.

Fabrizio did not testify at Manafort's August trial, nor was he on the prosecutors' witness list. He has not been charged with a crime.

Fabrizio's firm earned more than a quarter million dollars from Manafort for polling and surveys in Manafort's Ukraine operation in 2012 and 2013, according to foreign lobbying disclosures.

Since the trial, the prosecutors have appeared to focus even more on Manafort's Eastern European relationships, especially with Kilimnik, which apparently continued through the presidential campaign and after Trump was elected President.

Fabrizio's Ukrainian work with Manafort in 2013 overlapped with Kilimnik, according to public filings. At the time, Kilimnik was setting up Manafort's Kiev operation.

Prosecutors have said Kilimnik has ties to the Russian military intelligence agency that hacked the Democrats during the election, according to a US intelligence assessment. Kilimnik has become a clear focus of the ongoing Mueller investigation since prosecutors accused him of attempting to tamper with witnesses following Manafort's arrest.

Prosecutors charged Kilimnik with obstructing justice for contacting the potential witnesses last spring. Kilimnik lives in Russia, prosecutors say, and has not appeared in US court to respond to his indictment.

In a portion of the Manafort court filing this week, Manafort's lawyers inadvertently revealed Manafort met with Kilimnik in Madrid in 2017. The two men also discussed a Ukrainian peace plan while Manafort was serving as Trump's campaign chairman.

As prosecutors were building their case against Manafort, they aimed to flip his longtime deputy Gates from fighting criminal charges to cooperating. Gates had unparalleled insight to offer into Manafort's finances as well as the Trump campaign, having served as Trump's deputy campaign chairman and a leader of the inaugural committee.

Soon after Fabrizio spoke to Mueller's team last year, Gates began cooperating

Gates continues to assist Mueller in several ongoing investigations, according to prosecutors and his legal defense team.