A former FBI and cybersecurity official is leading an effort on behalf of BuzzFeed to verify allegations in the so-called Steele dossier on President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE, Foreign Policy reported Monday.

Anthony Ferrante, who now works at FTI Consulting, has led the investigation for months, Foreign Policy reported, citing four sources. Ferrante joined the FBI in 2005, and joined the National Security Council as a cybersecurity expert in 2015.

Ferrante's team has reportedly been tracking down documents and conducting interviews in an effort to verify certain claims in the dossier, which contains allegations about Trump’s ties to Russia. Much of the document remains unverified.

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The document has been a source of controversy, as it was funded partly by the Democratic National Committee and Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE’s presidential campaign.

It was at the center of a Republican memo released earlier this month that accused the FBI and Justice Department of abusing a key surveillance program. The document accuses senior Justice Department officials of improperly using information from the dossier to obtain surveillance warrants on former Trump campaign adviser Carter Page.

While Trump and some other Republicans have said the memo vindicates him in special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's probe, Democrats said the document contains cherry-picked information and is misleading.

Democrats compiled a countermemo they say refutes the points made in the first, but last week Trump declined to release it.

Ferrante, FTI and the special counsel’s office all declined to comment to Foreign Policy.

BuzzFeed was the first outlet to publish the dossier, which contains salacious allegations, a year ago.

Last month, Trump's personal lawyer, Michael Cohen, sued BuzzFeed News for defamation over the publication. BuzzFeed has stood by its decision, arguing the dossier was of significant public interest.