Attorney General   William Barr   appointed Texas U.S. Attorney John Bash in May to look into the unmasking requests from late 2016 and early 2017, which involved intercepted conversations between   Michael Flynn   — President   Donald Trump ’s former national security adviser — and Russia’s ambassador to the U.S. during the 2016 election.

The “unmasking” of names in classified documents is a common, legal practice that allows government officials with proper security clearance to better understand what they’re reading, the Post noted. During the Flynn unmasking, the   list of Obama officials involved   included Vice President Joe Biden, FBI Director James Comey and director of national intelligence James Clapper.

But Trump has attacked the practice as a conspiracy to undermine his administration.

“No one has ever been criminally prosecuted for unmasking,” Ned Price, a former CIA analyst who worked in the Obama administration,   told Reuters at the time   of Barr’s announcement. “That would be tantamount to pursuing criminal charges against an intelligence analyst for merely doing his job.”

The Post, citing anonymous sources familiar with Bash’s investigation, said his findings also focused on whether Obama-era officials provided information from the documents to reporters. But the investigation didn’t find the type of smoking gun the Trump administration could leverage into political points, the sources said.

The Department of Justice has so far declined to release the findings of the investigation.

Trump has been under scrutiny lately over his   efforts to pressure the Justice Department   to investigate his political opponents in the waning days of his reelection campaign. He has said this month that he is “very disappointed” in Barr and called for the quick release of a probe into the Obama administration’s efforts to investigate any possible collusion between Russia and the Trump administration.

The attorney general has said those results will not be available before the Nov. 3 election.

“That’s a disgrace,” Trump said in an interview with conservative radio host Rush Limbaugh earlier this month. “I think it’s a disgrace. It’s an embarrassment.”

The president’s efforts to influence the Justice Department for political purposes has worried those within the agency and outside legal analysts. Justice Department spokesperson Kerri Kupec told Fox News in May that the practice of “unmasking” wasn’t “inherently” wrong but said the administration was concerned about how often the requests were made in the Obama White House.

Reuters noted at the time that the   Trump administration has requested far more unmaskings   than his predecessor.

Bash said last week that   he would resign   from the Department of Justice and move into the private sector, an abrupt departure that surprised many in the agency.

“I hope that I have discharged my authority wisely and have improved the safety and security of my fellow Texans,” he said in a statement at the time. “I leave the Department with a profound respect for its people, its traditions, and its importance to our constitutional democracy.”