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Former FBI Director James Comey included a slew of sensitive and classified information in a series of comprehensive personal memos -- including not only the details of his conversations with President Trump, but also the "code name and true identity" of a confidential source, according to a court-ordered filing by the Justice Department late Monday.

The filing acknowledges that Comey maintained a far more detailed and lengthy private paper trail than was previously known, and that federal investigators apparently hoped to use Comey's contemporaneous, secretive writings to test the truthfulness of Trump's comments as part of a then-ongoing obstruction of justice inquiry.

Comey meticulously outlined "foreign intelligence information obtained from and through" the key human source, "information about whether the FBI initiated coverage through the Foreign Intelligence Surveillance Act (FISA) on a particular individual," relevant "sources and methods" used in the FBI's investigation, as well as "information concerning the President's foreign policy decisionmaking," according to the DOJ.

All of that information is "currently and properly classified," the DOJ noted.

Additionally, Comey's memos included documentation of "non-public interactions" between "specific foreign governments and officials" and U.S. government officials. Disclosing those details, the DOJ insisted, "could reasonably be expected" to "affect the United States' relationship with those countries."

Former FBI Director James Comey said “history has its eyes on us” and encouraged people to vote for Democrats in the midterm elections. (AP)

On Sunday, House Intelligence Committee ranking member Devin Nunes, R-Calif., announced a series of criminal referrals related to leaks and lies to Congress by a number of unnamed individuals -- and specifically singled out what he called the "horrific" leaks of the private conversations between Trump and the leaders of Australia and Mexico.

SOURCE: DOJ IS INVESTIGATING WHETHER COMEY'S MEMO LEAKS INCLUDED CLASSIFIED INFORMATION

The existence and contents of limited details from some of Comey's memos were partially leaked to the media by a Comey friend with Comey's knowledge following his termination, and served as a catalyst for Mueller's appointment in May 2017. Comey has denied that he leaked classified information in the memos. A review into the matter by the DOJ Inspector General (IG) is ongoing. a source tells Fox News, and Attorney General William Barr testifed on Tuesday that the DOJ is actively looking into the FBI's conduct.

The explanations Monday came amid a Freedom of Information Act (FOIA) lawsuit by CNN against the FBI, which seeks to publicly reveal not only the full contents of Comey's mysterious memos, but also the FBI's sealed explanations to a D.C. federal court in October 2017 as to why the memos needed to remain hidden from the public eye.

The FBI further disclosed on Monday that it had sought to keep Comey's writings hidden during Special Counsel Robert Mueller's Russia probe in part because releasing Comey's memos could "reasonably be expected to affect the testimony of people knowlegeable about the conversations" -- an apparent reference to Trump.

That comment came in a sealed declaration filed with a Washington, D.C. federal district court by then-FBI Deputy Assistant Director in the Counterintelligence Division David Archey on October 13, 2017, when multiple media reports indicated that Mueller was investigating the president for possibly obstructing justice.

FBI Deputy Assistant Director Peter Strzok is seated to testify before the the House Committees on the Judiciary and Oversight and Government Reform during a hearing on "Oversight of FBI and DOJ Actions Surrounding the 2016 Election," on Capitol Hill, July 12, 2018, in Washington. (AP Photo/Evan Vucci)

"Laying out a comprehensive case that Trump obstructed justice," read the title of one October 2017 column by Washington Post opinion writer Jennifer Rubin, who self-identifies as a conservative on Twitter.

The president later submited written answers to questions from Mueller's team, but did not agree to a sit-down interview. Trump's personal lawyer, Rudy Giuliani, repeatedly warned that investigators might set up a "perjury trap" and blame the president for making statements that, while truthful, were contested by other sources.

COMEY ADMITS HIDING MEMOS FROM SENIOR DOJ LEADERSHIP

Archey, who was the top FBI agent on Mueller's team following the removal of anti-Trump FBI agent Peter Strzok, was named last month to lead the FBI's Richmond, Va. field office.

Washington District Court Judge James E. Boasberg, an Obama appointee who was also tapped by Chief Justice John Roberts for a seat on the FISA court, issued an order last week demanding the FBI hand over "clean and redacted copies of the documents in dispute here," now that the Mueller probe has concluded.

That order apparently covered the Comey memos and documents relating to the declarations, and prompted the FBI's response filing on Monday.

UH-OH: AG BARR REVEALS HE'S REVIEWING FBI'S CONDUCT IN THE RUSSIA PROBE 

However, while the FBI agreed to reveal Archey's partially redacted declaration and another follow-up statement to the court, it argued that Comey's memos should remain sealed, in part because they contain classified or sensitive information.

The FBI also promised to file a follow-up to explain the redactions in the Archey declaration by next week.

TRUMP VOWS TO DECLASSIFY AND RELEASE FISA APP, RELATED DOCS NOW THAT MUELLER PROBE IS OVER

The Comey memos were more widely shared within the government than previously known, three sources familiar with the matter told Fox News last year -- although Comey later admitted to hiding the memos from some senior DOJ officials. Last April, the DOJ gave lawmakers redacted versions of five of the memos.

Public outrage centered on the news that Comey wrote in one of his memos that Trump had told him, "I hope you can let this go," amid reports that former National Security Adviser Michael Flynn had lied to the FBI and senior White House officials about his contacts with Russia's government.

Flynn was later charged with one count of lying to FBI agents in the White House. Prosecutors said they waived Foreign Agents Registration Act (FARA) charges related to Flynn's lobbying work in Turkey because of his cooperation.

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Trump, for his part, promised to "declassify and release" key FBI FISA warrant applications and related documents -- including the entirety of a FISA application to surveil a Trump aide that relied heavily on an unsubstantiated, leaked dossier created by an anti-Trump ex-British spy working for a firm hired by the Hillary Clinton campaign and Democratic National Committee. Leaked information about the dossier and the FISA application kickstarted the Russian collusion narrative.

As president, Trump has the unique authority to declassify and publicize not only the FISA materials, but also the Comey memos and the FBI's efforts to keep them hidden.

Mueller's investigation completed last month without securing the indictment of a single American for collusion with Russia or obstruction of justice -- "despite multiple offers from Russian-affiliated individuals to assist the Trump campaign."

Fox News' Catherine Herridge contributed to this report.