Updated

Attorney General Bill Barr has asked U.S. Attorney for the Western District of Texas John Bash to review the practice of "unmasking" before and after the 2016 presidential election, a controversy that has picked up steam after the Justice Department moved to drop charges against former National Security Adviser Michael Flynn, the DOJ told Fox News on Wednesday night.

Republican lawmakers have demanded more information about the extent of the practice after a previously clandestine list of Obama-era officials who sought to reveal what turned out to be the identity of Michael Flynn in intelligence reports was released earlier the month. The DOJ had moved to drop the Flynn case after internal memos were released raising serious questions about the nature of the investigation that led to his late-2017 guilty plea for lying to the FBI about his Russia contacts.

DOJ spokeswoman Kerri Kupec told Fox News' "Hannity" that U.S. Attorney John Durham, who has been reviewing the origins of the Russia investigation, was looking into "unmasking" but Barr determined certain aspects of the practice needed further review, and Bash has been assigned to do so.

Attorney General William Barr, left, has asked U.S. Attorney John Bash to review "unmasking" before and after the 2016 election.

Attorney General William Barr, left, has asked U.S. Attorney John Bash to review "unmasking" before and after the 2016 election. (File)

"Unmasking inherently isn't wrong, but certainly, the frequency, the motivation and the reasoning behind unmasking can be problematic, and when you're looking at unmasking as part of a broader investigation -- like John Durham's investigation -- looking specifically at who was unmasking whom, can add a lot to our understanding about motivation and big picture events," Kupec said.

Unmasking is a tool frequently used during the course of intelligence work and 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. In the typical process, when officials are requesting the unmasking of an American, they do not necessarily know the identity of the person in advance.

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Republicans became highly suspicious of the number of unmasking requests made by the Obama administration concerning Flynn, and have questioned whether other Trump associates were singled out.

The DOJ spokesperson also affirmed that the D.C. Court of Appeals has invited the DOJ to weigh in on the Flynn case, "and we will."

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Kupec maintained that the DOJ had the ability to drop the case against Flynn. "We have the prosecutorial discretion to make that decision."

Fox News' Brooke Singman and Gillian Turner contributed to this report.