(FOX) — A trove of documents related to the origins of the “Russiagate” probe, the U.S. intelligence community’s widely scrutinized investigation of alleged collusion between members of the Trump administration and Russia, will be declassified on Friday, a Senate source with knowledge of the situation told Fox News.

The declassified documents will include depositions, transcripts and interviews, the Senate source told Fox News Chief White House Correspondent John Roberts. The release is expected to include hundreds of documents.

Last October, then-Attorney General William Barr appointed U.S. Attorney for the District of Connecticut John Durham as special counsel to continue investigating the origins of the Russia probe. The investigation is focused on the conduct of FBI agents who investigated Trump’s Russia ties in an operation called “Crossfire Hurricane.”

Durham first began his probe shortly after special counsel Robert Mueller completed his year-long investigation into whether the Trump campaign colluded with Russia to influence the 2016 presidential election.

Trump and prominent allies have long referred to the Russia investigation as a “hoax” meant to undermine his presidency. In October, the president tweeted that he had “fully authorized the total Declassification of any & all documents pertaining to the single greatest political CRIME in American History, the Russia Hoax.”

“All Russia Hoax Scandal information was declassified by me long ago,” Trump said at the time. “Unfortunately for our Country, people have acted very slowly, especially since it is perhaps the biggest political crime in the history of our Country.”

Last year, the Senate Intelligence Committee published a five-part report detailing Russian interference in the 2016 presidential election. In the final volume, published last August, the committee said some of the Trump campaign’s contacts with Russian agents ahead of the 2016 presidential election were a “grave counterintelligence threat,” but “found no evidence” that Trump or members of his campaign colluded with Russia.

The committee also found that the FBI gave “unjustified credence” to allegations levied in the infamous Steele dossier, an unverified report compiled by former British intelligence officer Christopher Steele detailing Trump’s dealings with Russia.

Fox News’ Brooke Singman and the Associated Press contributed to this report.