Washington (CNN) Attorney General Jeff Sessions' private attorney said Wednesday that the attorney general is not under investigation by special counsel Robert Mueller's office for perjury related to statements made at his confirmation hearing.

In response to an ABC News report saying that now-dismissed FBI official Andrew McCabe had authorized an investigation into whether Sessions lied to Congress about his contacts with a top Russian diplomat, attorney Chuck Cooper said Mueller's office has informed him that Sessions is not being investigated over his testimony.

"The special counsel's office has informed me that after interviewing the Attorney General and conducting additional investigation, the Attorney General is not under investigation for false statements or perjury in his confirmation hearing testimony and related written submissions to Congress," Cooper said in a statement to CNN.

The special counsel's office declined to comment.

A source close to Sessions said he was not aware of any investigation into possible perjury when McCabe was fired last week.

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CNN reported in January that Sessions was questioned for several hours by Mueller's team as part of the investigation into Russian election meddling and any possible collusion with President Donald Trump's team. A source familiar with the matter told CNN that Cooper was unaware of any possible perjury investigation related to Sessions before it was revealed by the ABC report.

Sessions has repeatedly said that he didn't mislead senators or lie under oath.

Vermont Democratic Sen. Patrick Leahy and then-Minnesota Democratic Sen. Al Franken wrote to then-FBI Director James Comey last March asking the FBI to investigate Sessions' testimony. The ABC report said McCabe opened the probe after the letter.

A representative for McCabe declined to comment on the ABC story, which said top lawmakers of both parties were informed about the probe in a private briefing from McCabe in May, where Deputy Attorney General Rod Rosenstein also attended.

A spokesman for Leahy said Wednesday that the senator was "not otherwise made aware of an investigation" into Sessions for perjury and that the FBI had declined to "confirm or deny the existence of an investigation" as of May 2017.

Sessions confirmed last year that he met with Sergey Kislyak, the former Russian ambassador to the US, on two occasions: once on the sidelines of the Republican National Convention in July 2016, and then in his office in September 2016, when Sessions was a member of the Senate Armed Services committee.

Sessions did not, however, mention either meeting during his confirmation hearing last January -- a fateful choice that has cast a long shadow over his tenure at the Justice Department.

The critical exchange took place in January 2017, when Franken read from a CNN story about the dossier on Trump and Russia, and asked Sessions: "If there was any evidence that anyone affiliated with the Trump campaign communicated with the Russian government in the course of this (2016) campaign, what would you do?"

Sessions responded: "I'm not aware of any of those activities. I have been called a surrogate at a time or two in that campaign and I did not have communications with the Russians."

He further replied, "no," when asked whether he had been "in contact with anyone connected to any part of the Russian government about the 2016 election, either before or after Election Day" in his Senate questionnaire.

For over a year, the attorney general has faced scrutiny from lawmakers on Capitol Hill about those portions of his testimony.

After his confirmation hearing, The Washington Post reported on Sessions' undisclosed meetings with Kislyak, prompting members of Congress to call for Sessions to resign or step aside from overseeing the FBI's investigation into potential coordination between Russian officials and the Trump campaign.

Kislyak, a career diplomat, was considered to be one of Russia's top spies and spy-recruiters in Washington, according to current and former senior US government officials -- though Russian officials dispute that characterization. Ultimately, Sessions recused himself from all investigations related to the 2016 campaign and Mueller was appointed special counsel.

Sessions has steadfastly maintained that he was honest in his testimony.

"It simply did not occur to me to go further than the context of the question and list any conversations I may have had with Russians in routine situation, as a I had with numerous other foreign officials," Sessions said at a Senate Intelligence Committee hearing last June.

"I have never met with or had any conversations with any Russians or any foreign officials concerning any type of interference with any campaign or election," he added.

Sessions later said he did not recall a third alleged private meeting with Kislyak on April 27, 2016, at the Mayflower Hotel in Washington, where then-candidate Trump delivered his first major foreign policy speech.

Finally, in November, Sessions testified that he vaguely remembered a March 2016 meeting with Trump campaign aide George Papadopoulos, but said he had "no clear recollection of the details" of what was said at the time. Papadopoulos pleaded guilty last fall to making false statements to investigators about his interactions with foreign officials close to the Russian government.

"After reading (Papadopoulos' account), and to the best of my recollection, I believe that I wanted to make clear to him that he was not authorized to represent the campaign with the Russian government, or any other foreign government, for that matter," Sessions told House members. "But I did not recall this event ... and would gladly have reported it had I remembered it, because I pushed back against his suggestion."