Special Counsel Robert Mueller has impaneled a Washington, D.C. grand jury for his probe of Russia’s interference in the 2016 election, according to a Wall Street Journal report.

The Journal reported that this new development is “a sign that his inquiry is growing in intensity and entering a new phase.”

Mueller is investigating Russia’s efforts to influence the 2016 election and whether President Donald Trump’s campaign or associates colluded with Moscow.

On "Shepard Smith Reporting," one of the authors of the report, Del Quentin Wilbur, explained that grand juries are powerful investigative tools that allow prosecutors to subpoena documents, put witnesses under oath and seek indictments, if there is evidence of a crime.

Stephen Miller Rips CNN's Acosta for Revealing His 'Cosmopolitan Bias'

Boy Writes Letter to Trump Asking If He Can Mow the White House Lawn

"It's both a basic step, but also one that signals, 'Hey, this is heating up. I've found enough here to justify getting more information and doing more work,'" Wilbur said.

He added another sign the investigation is ramping up is that Greg Andres, a top partner at major New York law firm Davis Polk & Wardwell LLP, has joined Mueller’s team.

He said that no one of Andres' stature would leave a successful private practice to join an investigation that's soon going to die.

Wilbur pointed out, however, that this does not mean someone is being charged with a crime. It merely means that Mueller believes the grand jury is a necessary tool in the investigation.

Watch more above.

Cortes on 'Treasonous' New Leaks of Trump's Calls: 'The Swamp Is Hard to Kill'

'Prosecutors Would Be Interested in This': Judicial Watch Reveals More Clinton-Abedin Emails

Report: Al Gore's Home Uses 21x More Energy Than Average US Household