Former national security adviser Michael Flynn’s name was not actually masked in a key document detailing his calls with the Russian ambassador in late 2016, Fox News has confirmed.

A congressional source familiar with the surveillance told Fox News that Flynn’s name was not redacted in the initial report about his calls with then-Russian Ambassador Sergey Kislyak, and that his name from the unredacted transcript of the calls was then leaked to the press.

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The timeline of that activity already strongly suggested that the numerous, recently revealed requests to "unmask" Flynn pertained to other reports. The source noted that Flynn’s calls with Kislyak took place during the presidential transition period on Dec. 22, 2016 and Dec. 29, 2016. The source then noted that a majority of the known Flynn unmasking requests from top Obama officials came prior to Flynn’s calls with Kislyak on those dates.

According to the list of officials involved in requests to unmask Flynn's name, which was declassified by acting Director of National Intelligence Richard Grenell last week and made public by GOP senators, former U.S. Ambassador to the United Nations Samantha Power made five unmasking requests prior to Flynn’s first call with Kislyak — spanning Nov. 30, 2016 and Dec. 14, 2016. Power later made requests on Dec. 23, 2016 and Jan. 17, 2017.

Then-Director of National Intelligence James Clapper also made an unmasking request for Flynn on Dec. 2, 2016, which also was prior to the Kislyak conversations; then-CIA Director John Brennan made requests on Dec. 14 and Dec. 15, 2016; and then-FBI Director James Comey made a request on Dec. 15, 2016.

The list shows that more than two-dozen Obama administration officials made such unmasking requests prior to his calls with Kislyak on Dec. 22, 2016.

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Unmasking occurs after U.S. citizens' conversations are incidentally picked up in conversations with foreign officials who are being monitored by the intelligence community. The U.S. citizens' identities are supposed to be protected if their participation is incidental and no wrongdoing is suspected. However, officials can determine the U.S. citizens' names through a process that is supposed to safeguard their rights.

Senate Judiciary Committee Chairman Lindsey Graham, R-S.C., who is leading an investigation into the origins of the Russia probe, signaled this week that he will subpoena witnesses over the unmasking of Flynn. On Tuesday, Graham sent a letter to Grenell questioning why the list of Flynn unmasking requests “did not contain a record showing who unmasked” Flynn’s identity in the call with Kislyak.

But The Washington Post reported this week that it was the FBI, not the NSA, that wiretapped Kislyak’s phone calls and created the summary of the transcript.

According to the ODNI’s Office of Civil Liberties, Privacy and Transparency, a U.S. citizen's actual identity may be included in an intelligence report at the time it is first prepared and disseminated if such inclusion meets the agency’s minimization standard.

Former Assistant U.S. Attorney in the Southern District of New York Andrew McCarthy told Fox News on Thursday that because the FBI regarded Flynn as a "suspected clandestine agent of Russia," the agency "could have rationalized either that Flynn's conversation with Kislyak was itself foreign intelligence information, or that, because Kislyak was an agent of Russia, knowing Flynn's identity was necessary in order to understand and assess the importance of the information about Russia's activities and intentions."

McCarthy, earlier this week, first highlighted the absence of a record showing who unmasked Flynn in connection with his conversations with Kislyak.

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“There isn’t one,” McCarthy wrote in an op-ed. “I suspect that’s because Lt. Gen. Flynn’s identity was not 'masked' in the first place. Instead, his Dec. 29, 2016 call with Kislyak was likely intercepted under an intelligence program not subject to the masking rules, probably by the CIA or a friendly foreign spy service acting in a nod-and-wink arrangement with our intelligence community.”

Meanwhile, other intelligence agencies did produce reports that included information on Flynn in which his name was masked. The requests in the document declassified by Grenell would appear to refer to these reports, though it's not clear whether those involved in the requests even knew Flynn was the redacted name.

The declassified list of Obama officials who sought to unmask Flynn, prior to the Kislyak call, and after the call, included Power, Clapper, Brennan, Comey, then-Obama White House Chief of Staff Denis McDonough and then-Vice President Joe Biden.

DECLASSIFIED SUSAN RICE EMAIL SHOWS COMEY SUGGESTED 'SENSITIVE' INFO ON RUSSIA NOT BE SHARED WITH FLYNN

Meanwhile, data obtained by Fox News last week shows that thousands of unmasking requests have been fulfilled every year across both the Obama and Trump administrations, reflecting the often routine nature of these requests in intelligence work. The practice is regarded as an important national security tool, a view reflected by these numbers.

But Republicans are highly suspicious of the number of unmasking requests made concerning Flynn, and have questioned whether other Trump associates were singled out. The list released only covers the period of time between Election Day 2016 and the inauguration.

This week, Graham and Sen. Ron Johnson, R-Wis., have requested a list of unmasking requests spanning January 2016 through January 2017, related to officials connected to the Trump campaign and/or members of the Trump family. It is unclear when that could be released.

Flynn's calls would eventually lead to him 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. He later sought to withdraw that plea. The Justice Department recently moved to dismiss the case entirely.

Fox News' Gillian Turner contributed to this report.