The FBI is conducting an internal investigation into the bureau’s Trump-Russia investigation, also known as Crossfire Hurricane. 

The news of the internal review came during testimony from FBI Special Agent Curtis Heide Tuesday during the trial of Michael Sussmann — the first trial out of Special Counsel John Durham’s years-long investigation into the origins of the Trump-Russia probe.

Heide confirmed during testimony that he is being investigated for withholding potentially exculpatory information in a Foreign Intelligence Surveillance Act (FISA) warrant application to the Foreign Intelligence Surveillance Court.

Heide said Tuesday that the exculpatory information in question was a "recording from one of the subjects."

SPECIAL COUNSEL JOHN DURHAM'S PROSECUTION OF MICHAEL SUSSMANN: EVERYTHING YOU NEED TO KNOW

Special Counsel John Durham departs the U.S. Federal Courthouse

Special Counsel John Durham departs the U.S. Federal Courthouse after opening arguments in the trial of Attorney Michael Sussmann (REUTERS/Julia Nikhinson)

Fox News first reported in 2019 that Durham’s review was zeroing in on transcripts of recordings made by at least one FBI confidential human source who met with Trump campaign aide George Papadopoulos overseas in 2016, specifically looking at why certain "exculpatory" material from them was not presented in subsequent applications for FISA warrants against Page.

A source, in 2019, told Fox News that the "exculpatory evidence" that could be included in those transcripts, which were declassified and released in April 2020, was Papadopoulos denying having any contact with the Russians to obtain the supposed "dirt" on Clinton.

Fox News obtained the declassified transcript of the secretly recorded meeting in April 2020. The transcript revealed the confidential human source pressed Papadopoulos on whether the Trump campaign was involved in Russian election meddling — something that, the transcript shows, Papadopoulos emphatically denied.

DOJ’S RUSSIA PROBE REVIEW FOCUSING ON 'SMOKING GUN' TAPES OF MEETING WITH TRUMP AIDE: SOURCES

It is unclear if this is the "exculpatory" information Heide is under investigation for omitting from the FISA warrant applications.

The transcript, however, is of a more than 4-hour long conversation betweenPapadopoulos and a confidential FBI source on Oct. 31, 2016. According to the obtained transcripts, the confidential human source (CHS) met with Papadopoulos and asked whether he thought Russians hacked the Democratic National Committee (DNC) ahead of the Democratic National Convention.

FBI building

General view of the J. Edgar Hoover F.B.I. Building in Washington, U.S., March 10, 2019. REUTERS/Mary F. Calvert (REUTERS/Mary F. Calvert)

"No," Papadopoulos replied.

When asked whether he thought the Russians had "special interests" in the election, Papadopoulos said: "That’s all bullsh--. No one knows who’s hacking them," and added that it "could be the Chinese, could be the Iranians, it could be some Bernie, uh supporters. Could be anonymous."

Papadopoulos was then asked whether he thought Russians "have interest in Trump."

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"They, dude, no one knows how a president’s going to govern anyway. You don’t just say, oh I like—," he said before being cut off. "I don’t know. Even Putin said it himself. It’s all, it’s like conspiracy theories."

The source went on to press Papadopoulous, saying: "I feel like there’s some heavy Trump supporters out there that kind of want to rig this f—king election in Trump’s favor and then at the same time, I don’t know."

Papadopoulos quipped: "Dude, you, you… there is no rigging in his favor."

The source pushed him, once again, on whether he thought the Trump campaign had anything to do with hacking of the DNC.

"No, I know that for a fact," he said. "I’ve been working with them for the last nine months. That’s and all of this stuff has been happening, what, the last four months?"

The comments made by Papadopoulos were noteworthy because, according to officials, they were never provided or included in evidence to the Foreign Intelligence Surveillance Court (FISC) when seeking warrants and warrant renewals to surveil Trump campaign aide Carter Page over suspicion of Trump campaign ties to Russia.

George Papadopoulos, former Trump campaign advisor

George Papadopoulos, the former Trump campaign adviser who triggered the Russia investigation, arrives for his first appearance before congressional investigators, on Capitol Hill in Washington (AP Photo/Carolyn Kaster)

A Justice Department official in April 2020 confirmed the authenticity of the transcripts. The official, at the time, told Fox News that the transcript was just one of a series of productions that the Justice Department made in the wake of DOJ Inspector General Michael Horowitz's report on his review of misconduct of the Foreign Intelligence Surveillance Act (FISA).

Horowitz wrote in his report, released in December 2019, that "the FBI did not inform of these conversations at the time they occurred" and the "FISA renewal applications on Carter Page did not include these statements."

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The transcripts had been classified, but were declassified under former President Trump’s May 2019 move to approve declassification of documents related to the surveillance of his campaign during the 2016 election.

The FBI obtained FISA warrants against Trump campaign aide Carter Page. 

The now-discredited anti-Trump dossier which contained alleged ties between Donald Trump and Russia served as the basis for FISA warrants against him.

Carter Page

Former Trump adviser Carter Page. (Chip Somodevilla/Getty Images)

The dossier was commissioned by Fusion GPS — an opposition research firm hired by Clinton campaign general counsel Marc Elias to conduct research against Trump. It was authored by ex-British intelligence officer Christopher Steele, and paid for by Hillary Clinton’s presidential campaign and the Democratic National Committee through law firm Perkins Coie — where Elias and Sussmann were employed.

Sussmann has been charged with making a false statement to the FBI when he told Baker in September 2016, less than two months before the presidential election, that he was not doing work "for any client" when he requested and attended a meeting in which he presented "purported data and ‘white papers’ that allegedly demonstrated a covert communicates channel" between the Trump Organization and Alfa Bank, which has ties to the Kremlin.

Durham’s team alleges Sussmann was, in fact, doing work for two clients: the Hillary Clinton campaign and a technology executive, Rodney Joffe. Following the meeting with Baker, Sussmann billed the Hillary Clinton campaign for his work.

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Sussmann has pleaded not guilty to the charge. 

Meanwhile, Heide also testified Tuesday he was sent to Washington D.C. in 2016 to join the team investigating Hillary Clinton's private email server and handling of classified information. The FBI's codename for that probe was "Midyear Exam."