Department of Justice Inspector General Michael Horowitz said on Wednesday that he is "very concerned" about leaks from FBI field offices to Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE, President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE's personal lawyer, and other individuals.

Asked by Sen. Patrick Leahy Patrick Joseph LeahyBipartisan representatives demand answers on expired surveillance programs Democrats shoot down talk of expanding Supreme Court Battle over timing complicates Democratic shutdown strategy MORE (D-Vt.) about the appearance that Giuliani was getting "highly sensitive leaks" from the FBI's New York field office, Horowitz noted that unauthorized leaks were under investigation.

"As we noted publicly last year in our report, we were very concerned about that," Horowitz told the Senate Judiciary Committee.

"We are investigating those contacts. We've issued a couple of public summaries so far about people we've found violated FBI policy. We have other investigations ongoing," Horowitz continued.

He added that, while it has been hard to prove the substance of conversations between FBI and reporters or outside individuals, “we can prove the contacts."

"Under FBI policy, you need authorization if you're going to disclose information and have certain contacts," he said.

Former FBI Director James Comey James Brien ComeySteele Dossier sub-source was subject of FBI counterintelligence probe Judge will not dismiss McCabe's case against DOJ Democrats fear Russia interference could spoil bid to retake Senate MORE told a House committee last year that he was concerned the FBI's New York field office was leaking to Giuliani.

“I was concerned that there appeared to be in the media a number of stories that might have been based on communications reporters or non-reporters like Rudy Giuliani were having with people in the New York field office,” Comey testified at the time.

Sen. Dick Durbin Richard (Dick) Joseph DurbinHawley warns Schumer to steer clear of Catholic-based criticisms of Barrett Two Judiciary Democrats say they will not meet with Trump's Supreme Court pick Sunday shows preview: Lawmakers prepare for SCOTUS confirmation hearings before election MORE (D-Ill.) took a jab at Trump's lawyer on Wednesday when the topic resurfaced during the hearing.

"Mr. Giuliani now professes to be President Trump's lawyer and occasionally the president acknowledges that, sometimes he doesn't," Durbin said.

Durbin also asked Horowitz if there were "any concerns" that Giuliani is continuing to "improperly obtain" information from law enforcement sources.

Horowitz said that he was not investigating matters related to Ukraine, to which he believed Durbin was referring.

Horowitz is testifying on the IG report released this week on alleged surveillance by the FBI during the 2016 presidential campaign. The Hill is providing running updates on the hearing.

--This report was updated at 1:34 p.m.