Rep. Devin Nunes said the Justice Department inspector general may now be able to find out when British ex-spy Christopher Steele first briefed the FBI about his anti-Trump research as part of an investigation into alleged abuse of the Foreign Intelligence Surveillance Act.

The California Republican reacted to news Tuesday that DOJ Inspector General Michael Horowitz's team conducted a two-day interview with Steele, the author of the unsubstantiated and salacious dossier attacking President Trump that was used by the FBI to obtain FISA warrants to surveil onetime Trump campaign aide Carter Page.

Although Nunes called this a "good development," he also said there is one significant caveat that stands in the way of a potential breakthrough considering he believes Steele's sources are dubious at best.

"[Horowitz is] looking at the origins of the investigation but at least by talking to Christopher Steele, if Steele is being honest, which is a big if, he may know when it was that Steele was first briefing FBI agents," Nunes said on Fox News @ Night.

Four FISA warrant applications and renewals were filed from October 2016 through June 2017 against Page. The applications relied heavily on the unverified dossier compiled by 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. Steele and Fusion GPS shopped the research around to various government figures, including one skeptical State Department official, as well as the media in the run-up to the 2016 election.

Nunes, the top Republican on the House Intelligence Committee, has long been skeptical of the FBI's assertion that its counterintelligence investigation, called Crossfire Hurricane, began in July 2016 following a tip from Australian diplomat Alexander Downer that he heard from Trump campaign adviser George Papadopoulos that the Russians had damaging information about Hillary Clinton.

He singled out Downer and Joseph Mifsud, a mysterious Maltese academic who first told Papadopoulos that the Russians had "dirt" on Clinton and who Nunes suspects is a Western intelligence plant, played in the series of events that effectively set in motion what would become the Russia investigation.

"It's just highly improbable that they didn't have pieces of Steele's phony work before that," Nunes told host Shannon Bream, noting how the dossier was actually a series of installments that could have been shared piecemeal. Steele met reportedly with an FBI official in Rome in the summer of 2016, but, as noted in a Democratic rebuttal memo to GOP's House Intelligence Committee memo on alleged government surveillance abuses, Steele's reporting did not reach the counterintelligence team at FBI headquarters until mid-September.

Nunes said if Steele wants to clear his name, he needs to testify before Congress.

Nunes said in an interview late last month that he wants to ask Robert Mueller how far the counterintelligence investigation into Trump's campaign goes when the former special counsel of the Russia investigation testifies on July 17. Democrats have dismissed the GOP's excitement about Horowitz's inquiry and Steele's role in it as "whataboutism" run amok.

A second development related to Horowitz's inquiry on Tuesday was the revelation of a letter the watchdog sent to Congress last month that said his team has “received and reviewed over one million records” and has “conducted over 100 interviews, including [with] current and former DOJ and FBI personnel” during its inquiry. Horowitz also said his team has “made substantial progress towards completing the review" and that he would provide another update about the timeline for the release of the final report “in the coming weeks.”

Last week House Judiciary Committee member John Ratcliffe of Texas said that he had met with Horowitz in late June and the inspector general said his investigation had concluded. This was followed by a Fox News report that said at least one key witness who is not part of the DOJ or the FBI came forward only after Attorney General William Barr tasked U.S. Attorney John Durham of Connecticut to lead a review of the origins of the Russia investigation. It now appears Steele was the subject of this "breakthrough."

The DOJ's review of the early stages of the Russia investigation is not a criminal inquiry, but should Durham find criminal activity, he can take prosecutorial action.