At least one key witness in the Justice Department inspector general's investigation into potential abuse of the Foreign Intelligence Surveillance Act came forward as the inquiry was winding down.

The individual, who is not part of the Justice Department or FBI, only did so after Attorney General William Barr tasked U.S. Attorney John Durham of Connecticut to lead a review of the origins of the Russia investigation, according to Fox News. It is unclear whether this "breakthrough" was actually due to Barr's appointment.

The report did not identify the witness, but it follows reporting that British ex-spy Christopher Steele agreed a month ago to meet with inspector general Michael Horowitz's team. Steele's dossier, which contained salacious and unverified claims about President Trump's ties to Russia and was funded by Democrats, was used by the FBI obtain a series of FISA warrants to wiretap one-time Trump campaign adviser Carter Page.

Sources said fresh developments led to Horowitz to reinterview some witnesses.

Earlier this week, House Judiciary Committee member John Ratcliffe of Texas said he met with Horowitz and learned that the FISA abuse investigation had been wrapped up after the inspector general appeared to miss Barr's prediction for a late May or early June completion. He said Horowitz's team is "in the process of drafting that report" but cautioned that their findings may not be released for at least a month. A representative for Horowitz declined to comment on the status of the inspector general investigation to Fox News.

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.