Russia probe files released as part of the Justice Department's move to drop its case against former National Security Adviser Michael Flynn are raising new questions about a mysterious Inauguration Day email sent by Flynn's predecessor in the Obama administration, Susan Rice.

An exhibit in the DOJ's motion to dismiss the Flynn case last week detailed a special counsel interview of former Deputy Attorney General Sally Yates. The interview indicated outgoing President Barack Obama was aware of Flynn’s intercepted December 2016 phone calls with then-Russian Ambassador Sergey Kislyak during the presidential transition period.

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The document noted Yates learned about the calls during a Jan 5, 2017, Oval Office meeting with Obama, Rice, then-FBI Director James Comey, then-CIA Director John Brennan, and then-Director of National Intelligence James Clapper.

After the briefing, Obama asked Yates and Comey to "stay behind," and said he had "learned of the information about Flynn" and his conversation with Russia's ambassador about sanctions. Obama "specified that he did not want any additional information on the matter, but was seeking information on whether the White House should be treating Flynn any differently, given the information.”

At that point, the document said, "Yates had no idea what the president was talking about, but figured it out based on the conversation. Yates recalled Comey mentioning the Logan Act, but can't recall if he specified there was an 'investigation.' Comey did not talk about prosecution in the meeting.”

This would eventually lead to Flynn being interviewed, amid supposed concern he had violated the obscure and never-successfully-enforced Logan Act, and later pleading guilty to lying to investigators about his Kislyak talks.

But the mention of that Oval Office meeting aligns with an email that Rice — on Jan. 20, 2017, the day President Trump was sworn into office — sent herself documenting Obama’s guidance, evidently in the same meeting, about how law enforcement should investigate Russian interference in the 2016 presidential race.

Rice's office downplayed the significance of that email when it first surfaced in early 2018, raising questions at the time from congressional Republicans.

A source close to the Senate Judiciary Committee told Fox News on Monday that GOP Senate investigators are now taking a closer look at that email.

Ambassador Susan Rice, former National Security Advisor to President Barack Obama, speaking at the J Street National Conference in Washington, DC on April 16, 2018 (Photo by Michael Brochstein/Sipa USA)(Sipa via AP Images)

Susan Rice, who served as the National Security Advisor under former President Barack Obama, has been critical of Trump's relationship with Russia. (AP Photo)

The message was first flagged in 2018 by Sens. Chuck Grassley, R-Iowa, the former Senate Judiciary Committee chairman, and Lindsey Graham, R-S.C., who now sits as chairman of the panel. The email was partially unclassified and appeared to detail that same Jan. 5, 2017, meeting, also said to include former Vice President Joe Biden.

“President Obama began the conversation by stressing his continued commitment to ensuring that every aspect of this issue is handled by the intelligence and law enforcement communities ‘by the book,’” Rice emailed to herself. “The president stressed that he is not asking about, initiating or instructing anything from a law enforcement perspective. He reiterated that our law enforcement team needs to proceed as it normally would by the book.”

The email also appeared to reflect Obama’s guidance on sharing sensitive information with both the Russians and the incoming Trump administration.

Rice wrote that Obama said, “he wants to be sure that, as we engage with the incoming team, we are mindful to ascertain if there is any reason that we cannot share information fully as it relates to Russia.”

She added: “The President asked Comey to inform him if anything changes in the next few weeks that should affect how we share classified information with the incoming team. Comey said he would.”

At the time of discovery, Graham described Rice's email as "disturbing."

“She’s sending herself an email talking about a conversation on Jan. 5 with the president, reassuring herself, and I guess the president, that this would be done by the book,” Graham told Fox News in February 2018. “I think that’s odd and disturbing because we know the investigation regarding the Trump campaign was anything but by the book.”

But Rice’s attorney at the time, Kathryn Ruemmler, said there was “nothing ‘unusual’” about Rice “memorializing an important discussion for the record.”

“The Obama White House was justifiably concerned about how comprehensive they should be in their briefings regarding Russia to members of the Trump transition team, particularly Lt. General Michael Flynn, given the concerning communications between him and Russian officials,” Ruemmler said in a statement to Fox News in 2018. “The discussion that Ambassador Rice documented did not involve the so-called Steele dossier.”

Ruemmler added: “Any insinuation that Ambassador Rice’s actions in this matter were inappropriate is yet another attempt to distract and deflect from the importance of the ongoing investigations into Russian meddling in America’s democracy.”

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The renewed focus on Rice’s email comes after House Intelligence Committee Chairman Adam Schiff, D-Calif., also released a trove of thousands of pages of transcripts of interviews with former Trump campaign officials and Obama administration officials from the panel’s own Russia investigation.

The transcripts, which included Rice’s interview with the panel in 2017, revealed that top Obama officials were questioned over whether they had or had seen evidence of collusion, coordination or conspiracy between the Trump campaign and Russia during the 2016 election—the issue that drove the FBI’s initial case and later Special Counsel Robert Mueller’s investigation. Most said they had not.

“To the best of my recollection, there wasn’t anything smoking, but there were some things that gave me pause,” Rice said, according to her transcribed interview, in response to whether she had any evidence of conspiracy. “I don’t recall intelligence that I would consider evidence to that effect that I saw…conspiracy prior to my departure.”

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When asked whether she had any evidence of “coordination,” Rice replied: “I don’t recall any intelligence or evidence to that effect.”

When asked about collusion, Rice replied: “Same answer.”

Meanwhile, Obama’s unexpectedly intimate knowledge of the details of Flynn’s calls raised new questions about Obama’s awareness and role in the early days of the Russia investigation.

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The exhibit on the Yates interview continued: "It was not clear to Yates from where the President first received the information. Yates did not recall Comey's response to the President's question about how to treat Flynn. She was so surprised by the information she was hearing that she was having a hard time processing it and listening to the conversation at the same time.”

Yates, who was fired by the Trump administration after refusing to defend its travel ban executive order in court, would later say that she was concerned Flynn would be vulnerable to blackmail because of his interactions with Russia.

The filing to dismiss the Flynn case came after the DOJ determined that the bureau's 2017 Flynn interview -- which formed the basis for his guilty plea of lying to investigators -- was "conducted without any legitimate investigative basis.”

The retired Army lieutenant general for months had been trying to withdraw his plea, aided by a new attorney aggressively challenging the prosecution’s case and conduct.

Fox News' Gregg Re and Alex Pappas contributed to this report.