GOP Sens. Chuck Grassley and Ron Johnson requested information Wednesday on the “unmasking” of U.S. citizens by Obama administration officials during the time of the 2016 election and the presidential transition in 2017.

Grassley, R-Iowa, and Johnson, R-Wis., penned a letter to acting Director of National Intelligence Ric Grenell and Attorney General Bill Barr regarding the declassification of files related to the unmasking process.

GRENELL DECLASSIFIES NAMES OF OBAMA OFFICIALS WHO 'UNMASKED' FLYNN

As Fox News previously reported, Grenell made the decision to declassify information about Obama administration officials who were involved in the “unmasking” of former national security adviser Michael Flynn — whose calls with the former Russian ambassador during the presidential transition were picked up in surveillance and later leaked. Grenell appeared to have delivered those files to the DOJ last week.

“Based on recent press reports, it is our understanding that you conducted a classification review and declassified information related to numerous requests to ‘unmask’ the names of U.S. persons who appeared in certain intelligence reporting around the time of the 2016 election through January 2017,” Grassley and Johnson wrote. “We wholeheartedly agree that transparency is needed more now than ever.”

The senators noted that one of the most “significant unanswered questions” is “how many Americans were ‘unmasked,’ at whose request, and for what purpose.”

“We firmly believe that the best way to resolve these issues is to determine the truth, and to make clear to the American people what did and did not occur,” they wrote.

Grassley and Johnson “respectfully request that you make available to us, as soon as possible, all information regarding the ‘unmasking’ of U.S. persons requested by members of President Obama’s administration around the time of the 2016 election through January 2017.”

The request comes amid a back-and-forth between the Office of the Director of National Intelligence and the Justice Department over who should make the call on whether to actually release the documents that Grenell declassified.

The DOJ official told Fox News that the Justice Department currently has no plans to release that list of names.

Fox News is told the ODNI is the owner of that information, and if they want to release it they can do so. "That's their call," a source said.

JUSTICE DEPARTMENT REVIEWING 'UNMASKING,' BUT SOURCE SUGGESTS DECISION ON RELEASING FILES IS DNI'S CALL

The Justice Department’s stance comes after Grenell decided to declassify information about Obama administration officials who were behind the “unmasking” of Flynn.

The unmasking concerns events between the November 2016 election and Inauguration Day 2017, Fox News is told.

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.

Meanwhile, Fox News confirmed that a new round of documents is expected in the wake of a document dump last week that renewed focus on the Russia investigation and specifically the treatment of Flynn.

Another source familiar with the intelligence told Fox News that Grenell is moving to declassify several pieces of intelligence in stages, with this one being part of it. Asked if former President Barack Obama’s name is on the list of officials involving in unmasking Flynn, the source would not say, but stressed that the list would make waves.

Officials in the Obama administration have acknowledged that they moved to unmask some Americans in intelligence reports, but insisted that their reasons were legitimate. Those officials include Obama national security adviser Susan Rice, former ambassador to the United Nations Samantha Power and former deputy national security adviser Benjamin Rhodes.

A Justice Department official told Fox News this week that the DOJ has been reviewing the unmasking of U.S. officials as part of its broader examination of the origins of the Trump-Russia investigation and is taking a look at the files that Grenell declassified and delivered to the Justice Department last week.