A newly uncovered letter from the Justice Department’s inspector general to Congress revealed the DOJ watchdog has “received and reviewed over one million records” and has “conducted over 100 interviews, including current and former DOJ and FBI personnel” during its inquiry into alleged abuse of the Foreign Intelligence Surveillance Act.

Michael Horowitz, the head of the DOJ’s Office of Inspector General, sent the letter in late June to the chairman and ranking members of the Senate Judiciary and Senate Homeland Security committees, as well as to the chairman and ranking members of the House Judiciary and Oversight committees. The letter, first obtained by the Daily Caller, explained that his investigators “have made substantial progress towards completing the review.”

Horowitz and his team have been looking into whether the FBI and the DOJ abused the FISA process when they filed four applications and renewals beginning in October 2016 to surveil Trump campaign adviser Carter Page. The applications relied heavily on the unverified dossier compiled by British ex-spy Christopher Steele, who was hired by Fusion GPS. The opposition research firm was hired by Marc Elias of the Perkins Coie law firm at the behest of the Clinton presidential campaign.

“The [Office of Inspector General] has been working diligently on this review since its initiation on March 28, 2018,” Horowitz wrote. “As in all of our projects, my direction to our team has been to follow the evidence wherever it leads and to complete the review as quickly as possible.”

Horowitz’s letter also said that his team had been working to meet with “additional witnesses” to make sure that their effort was “thorough and complete.” New reports from earlier on Tuesday indicated that the DOJ watchdog’s attorneys had met with Steele in London earlier in June and had found at least some of Steele’s information new and useful. The reports indicated that Horowitz may have extended the investigation as a result of what it learned from Steele. Attorney General William Barr said earlier this year that he’d expected this inquiry to wrap up in May or June.

“The review has been complicated by other factors, such as the current classification level of virtually all of the information we have obtained and the fact that many witnesses are no longer government employees,” Horowitz continued in his letter. “Nevertheless, our investigative work is nearing completion, and we have been in the process of drafting our report for some time.”

Horowitz told the members of Congress that, when his draft report is done, he will follow the “usual process” to make sure the document is accurate, complete, and appropriately classified.

And the DOJ watchdog said he planned on letting them know about the timeline for the release of the final report “in the coming weeks.”

Horowitz had reportedly been homing in on Steele for months, and sources close to Steele expressed his willingness to meet with Horowitz in June.

Special counsel Robert Mueller’s team reportedly met with Steele twice in September 2017, and Steele also provided a written statement to the Senate Intelligence Committee in August 2018.

Republicans in Congress have long cast doubt on the credibility of Steele’s dossier, but they are not the only ones. Watergate journalist Bob Woodward has been calling it “garbage” for more than two years, and former CIA Moscow station chief Daniel Hoffman told the Washington Examiner that “I called what bullsh-t the dossier was a year-and-a-half ago … It’s likely FSB [the successor agency to the KGB] disinformation.”

A number of Steele’s biggest claims, including the allegation stemming from “Kremlin insiders” that former Trump lawyer Michael Cohen had met in Prague with Putin associates and foreign hackers, were knocked down in Mueller's report.

Other possible targets of the DOJ inspector general's inquiry likely included the approvers and signers of the four FISA warrant applications and renewals from October 2016 through June 2017, including former FBI Director James Comey, former FBI Deputy Director Andrew McCabe, former Deputy Attorney General Sally Yates, former Deputy Attorney General Rod Rosenstein, and the former acting Attorney General and now current FBI General Counsel Dana Boente, the only signer of a Page FISA application who is still in office.

Horowitz’s last high-profile investigation, which looked into the handling of the Clinton email investigation by the DOJ and FBI, resulted in a 568-page report released in June 2018.