Robert Mueller's Team Interview Trump Dossier's Christopher Steele

Special Counsel Robert Mueller's team of investigators have reportedly interviewed Christopher Steele, the former British spy, who compiled the Trump dossier. Aaron P. Bernstein/Reuters

Investigators examining the alleged ties between President Donald Trump and Russia have interviewed the former British spy who compiled a notorious dossier that contained a number of salacious claims about the President's actions in the run-up to the 2016 election.

Investigators from special counsel Robert Mueller's team met with Christopher Steele in Europe recently, a source familiar with the investigation told the Associated Press Friday. Two sources originally told CNN about the meeting. A source close to the ex-spy also confirmed the meeting to NBC News.

On Wednesday Reuters reported Mueller has begun probing claims made in the dossier about the Trump campaign's financial and personal ties to a number of Russians named in the document. American intelligence says many of these people are Russian spies or working for the Russian government.

Mueller has taken over the FBI's inquiries into the document as he leads an independent investigation on behalf of the Department of Justice looking at whether the Trump campaign assisted Russia's efforts to interfere in the 2016 presidential election.

Senior military and intelligence officials in the Trump administration say they agree with findings in a January report by key American intelligence agencies that Moscow directed a misinformation and hacking campaign to tilt the U.S. election.

Information from Steele could establish whether contacts between Trump campaign members and associates and those named in the document broke the law.

Read more: Trump-Russia "pee tape" dossier is now being investigated by special counsel Robert Mueller

Among other things, the document alleges Trump's former campaign chief Paul Manafort, political operative Carter Page, and Trump's personal lawyer Michael Cohen played a role in procuring damaging information on Trump's campaign rival Hillary Clinton with assistance from the Kremlin.

Trump has called the document "totally made-up facts by sleazebag political operatives." The document was released in full by BuzzFeed News in January with a warning the publication had not corroborated the findings.

Steele, who was formerly stationed in Russia with MI-6, heads a business intelligence firm in London that was hired to compile the document by the political research firm Fusion GPS. Funding originally came from both Republican and Democrat backers during the election but, even after the money ran out, Steele is reported to have continued his research because of what he found.

One of the firm's partner's, Glenn Simpson, was interviewed privately by the Senate Judiciary Committee in late August. The committee is one of three congressional bodies conducting inquiries into Russian election meddling, including the Senate and House Intelligence Committees.

In a statement in July to the Senate Judiciary Committee, Fusion GPS said: "Let's be clear about what's really happening: the President's political allies are targeting Fusion GPS because the firm was reported to be the first to raise the alarm over [the] Trump campaign's links to Russia."

Three Russians named in the document filed a libel lawsuit in the U.S. against Fusion GPS early this week claiming their reputations have been damaged by the firm.

The document's most salacious claim focuses on Trump's visit to Moscow in 2013 for the Miss Universe pageant, and alleges that the future president ordered prostitutes to soil a bed that President Barack Obama and his wife Michelle slept in at a luxury Moscow hotel. The claim is unverified.