The investigation into the investigators is heating up.

U.S. Attorney John Durham of Connecticut has met repeatedly with Attorney General William Barr since he was tasked last month with leading a review of the origins of the Russia investigation and the Justice Department's and FBI's conduct.

Sources tell Fox News that Durham is "very dialed in" and "asking all the right questions."

One major focus of his review is potential Foreign Intelligence Surveillance Act abuse, which is the subject of a separate investigation by DOJ Inspector General Michael Horowitz and is expected to conclude soon. British ex-spy Christopher Steele, whose unverified dossier was used in FISA applications to justify surveillance of former Trump campaign adviser Carter Page, has expressed a willingness to meet with Horowitz, but not with Durham.

During the 2016 election, Steele was working for the opposition research firm Fusion GPS, which received funding through the Perkins Coie law firm from the Clinton campaign and the Democratic National Committee. Steele's Democratic benefactors were not revealed to the Foreign Intelligence Surveillance Court.

Should Durham find criminal activity during the course of his investigation, sources said he would take charge of any prosecutions.

Durham, a Trump nominee who hails from Connecticut, has a reputation as a dogged and unbiased investigator handling difficult and controversial cases, including the prosecution of mobsters.

Barr's examination of the early stages of the counterintelligence investigation into Trump's campaign has been cheered by Republicans and criticized by Democrats. After President Trump granted Barr sweeping powers to declassify secret information, House Intelligence Chairman Adam Schiff panned the effort as a scheme to discredit special counsel Robert Mueller. Trump's order, which also instructed several agencies to cooperate with Barr, “represents a disturbing effort” to politicize intelligence and “raises grave concerns about inappropriate and misleading disclosures of classified information,” the California Democrat wrote in letters to U.S. intelligence leaders.

In a recent interview with CBS News, Barr said he chose Durham because he wanted "someone who is tenacious, who is used to looking at sensitive material involving government activities, who has a reputation for being fair and evenhanded."

He also revealed that U.S Attorney John Huber, who had been assigned by Barr's predecessor Jeff Sessions to look into issues related to FISA applications and the electronic surveillance, had "stood back" while Horowitz carried out his review.

Sessions also asked Huber in 2017 to look into issues related to the sale of Uranium One and allegations that former Secretary of State Hillary Clinton had been improperly involved in the process, as well as broader claims of corruption at the Clinton Foundation. Barr suggested Huber might soon reveal findings from that inquiry.

"The other issues [Huber has] been working on relate to Hillary Clinton” are "winding down and hopefully we'll be in a position to bring those to fruition," Barr said.