Justice Department Inspector General Michael Horowitz has officially completed his investigation into alleged Foreign Intelligence Surveillance Act abuses by the Justice Department and the FBI.

Rep. Doug Collins, the top Republican on the House Judiciary Committee, revealed in a letter Thursday that Horowitz notified Attorney General William Barr of the completion of his investigation earlier in the day.

Horowitz said in a letter to congressional leaders that his team is in the "process of finalizing our report by providing a draft of our factual findings to the Department and FBI for classification determination and marking." Once redactions are made and the report is returned to the inspector general, Horowitz's team will "proceed with our usual process for preparing final draft public and classified reports, and ensuring that appropriate reviews occur for accuracy and comment purposes."

Horowitz's team examined the FISA application and three renewals beginning in October 2016 to surveil former Trump campaign adviser Carter Page. The applications relied on the unverified dossier compiled by British ex-spy Christopher Steele, who was hired by opposition research firm Fusion GPS and funded by Democrats.

Republicans have alleged the FBI and the Justice Department misled the Foreign Intelligence Surveillance Court about the dossier's Democratic benefactors, which included Hillary Clinton's 2016 campaign and the Democratic National Committee, and its author's anti-Trump bias were left out of the FISA applications, and they have demanded accountability. Democrats countered that the FBI acted appropriately, saying the Justice Department and the FBI met the rigor, transparency, and evidentiary basis for probable cause.

Meanwhile, Barr's "investigation into the investigators" is underway, and the attorney general has said he is working very closely with Horowitz. The inspector general can recommend prosecutions, and U.S. Attorney John Durham, whom Barr tasked to lead the review of the origins of the Russia investigation, has the ability to convene a grand jury and subpoena people outside the government.

Collins said his committee "must act swiftly to address concerns outlined in the Inspector General’s report" and implored Judiciary Chairman Jerry Nadler to hold a hearing with Horowitz and FBI Director Christopher Wray. Nadler, confronted by GOP Rep. Jim Jordan earlier this week, said a hearing with Horowitz will happen at the "appropriate time."

The FISA filings required approval from top members of the FBI and the Justice Department; targets of Horowitz's inquiry likely included the approvers of the four applications and renewals: former FBI Director James Comey; former Deputy Attorney General Sally Yates; Dana Boente, the only signatory in active government service and currently Trump’s top lawyer at the FBI; then-FBI Deputy Director Andrew McCabe; and then-Deputy Attorney General Rod Rosenstein, who appointed former FBI Director Robert Mueller to be special counsel the month before.

The 412 pages of redacted FISA documents released in 2018 show the Justice Department and the FBI made extensive use of Steele’s unverified dossier, which he put together in 2016 at the behest of the opposition research firm Fusion GPS. The Clinton campaign hired the firm through Marc Elias of the Perkins Coie law firm and was briefed about Steele's findings throughout the race.

The Justice Department inspector general said when he launched the investigation last year at the behest of then-Attorney General Jeff Sessions he would “examine the Justice Department’s and the FBI’s compliance with legal requirements" related to FISA filings against Page and review the DOJ’s and the FBI’s dealings with Steele.

In his letter Friday, Horowitz divulged the expansive scope of his investigation.

"As I noted in my June correspondence to you, my direction to our team has been to follow the evidence wherever it leads and to complete the review as quickly as possible. Consistent with this guidance, the team has reviewed over one million records and conducted over 100 interviews, including several of witnesses who only recently agreed to be interviewed," the inspector general said.

The Justice Department declined to comment to the Washington Examiner.

The Steele dossier's central thesis was "a well-developed conspiracy of co-operation" between the Trump campaign and Russia, but Mueller didn't agree. Although Mueller concluded the Russians interfered in the 2016 presidential election, the investigation did not establish the Kremlin and Trump's campaign criminally conspired. Mueller’s report also shot down at least one of Steele’s biggest claims — that Trump lawyer Michael Cohen met with foreign hackers in Prague.

Horowitz reportedly “homed in” on Steele, and his team reportedly interviewed the ex-spy in June.