James Comey. Justin Sullivan/Getty Images The FBI is using the explosive but unverified collection of memos detailing allegations of collusion between President Donald Trump's campaign team and Russia as a "roadmap" for its investigation into Russia's interference in the 2016 presidential election, the BBC's Paul Wood reported Wednesday.

"The roadmap for the investigation, publicly acknowledged now for the first time, comes from Christopher Steele, once of Britain's secret intelligence service MI6," wrote Wood, one of the journalists who obtained a copy of Steele's dossier before it was published in full by BuzzFeed in January.

Some of the dossier's claims — many of which appear to align with events during the campaign — are slowly being corroborated. CNN reported earlier this month that the FBI had information to suggest that the Trump campaign "communicated with suspected Russian operatives to possibly coordinate the release of information damaging to Hillary Clinton's campaign."

Another key detail in the dossier has now been verified, according to the BBC: Mikhail Kalugin, a Russian diplomat who was withdrawn from Washington, DC, in August, was known to the US government as a Russian spy and had been under surveillance by the US intelligence community before being recalled.

Kalugin left the US while the FBI, which began receiving Steele's reports in June, was examining his role in funding Russian hackers who broke into the Democratic National Committee servers, McClatchy reported.

According to the dossier, Kalugin "had been withdrawn from Washington at short notice because Moscow feared his heavy involvement in the US presidential election operation ... would be exposed in the media there."

The FBI may be taking cues from Steele's dossier because it has worked with him in the past, according to Wood. Steele, who cultivated an extensive network of Russian sources during his time on MI6's Moscow desk, apparently worked with the FBI on Russia- and Ukraine-related matters between 2013 and 2016 — specifically with the FBI's Eurasian Joint Organized Crime Squad, according to a lengthy profile in Vanity Fair.

The squad "was a particularly gung-ho team with whom Steele had done some heady things in the past," Vanity Fair reported. "And in the course of their successful collaboration, the hard-driving FBI agents and the former frontline spy evolved into a chummy mutual-admiration society."

The relationship was so "chummy" that the FBI offered to pay Steele to continue his work in October, The Washington Post reported last month.

"Steele was known for the quality of his past work and for the knowledge he had developed over nearly 20 years working on Russia-related issues for British intelligence," The Post reported.

Some of the dossier's more outlandish claims, including salacious accounts of sexual escapades, have not been confirmed. Trump has dismissed the dossier as "phony stuff" and "fake news."

But comparing Steele's reports, which were written between June and December, with events that unfolded before and after the election reveals a series of coincidences that has added to questions surrounding Russia's interference in the election.