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Robert Mueller, the special counsel overseeing the Russia investigation, has impaneled a grand jury in Washington, The Wall Street Journal reported Thursday.

The move signals the investigation is ramping up, people familiar with the matter told the paper.

“This is yet a further sign that there is a long-term, large-scale series of prosecutions being contemplated and being pursued by the special counsel,” Stephen I. Vladeck, a law professor at the University of Texas, told the WSJ.

A spokesman for Mueller declined to comment to the WSJ. President Trump has repeatedly called the probe a “witch hunt” and denied any wrongdoing.

Also Read: Kellyanne Conway Says Robert Mueller's Team Wanted Hillary Clinton to Win (Video)

Ty Cobb, special counsel to the president, said he wasn’t aware of Mueller’s decision to impanel a grand jury, telling the WSJ: “The White House favors anything that accelerates the conclusion of his work fairly. … The White House is committed to fully cooperating with Mr. Mueller.”

Grand juries are a powerful way for prosecutors to subpoena documents and question witnesses. The move may suggest Mueller believes he will need to subpoena records and take testimony.

Federal prosecutors have been using at least one other grand jury in Alexandria, Va. in their criminal investigation of Michael Flynn. Mueller has taken over that investigation.

Also Read: Trump Blasts Russia Probe as 'Witch Hunt,' Suggests Robert Mueller 'Very Bad and Conflicted'

The WSJ cites another sign the investigation is ramping up: Greg Andres, a top partner in a powerful New York law firm has been hired by Mueller.

Mueller, a former FBI Director, has been charged with investigating Russian attempts at influencing the 2016 presidential election as well as possible collision between the Trump campaign and the Kremlin.

Mueller was appointed after Trump fired former FBI chief James Comey.

37 Hollywood Stars for Donald Trump (Photos)

Hillary Clinton had far more celebrity supporters than Donald Trump, but his 37 celebrity fans turned out to be the ones who backed the winning candidate. Here are Trump's celebrity fans.
“I’m not someone who’s saying he’s the best of this group. I’m saying I like this guy" – Jon Voight
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"I'm digging Trump ... My feeling: let the motherf---ing business guy run it like a f---ing business" –Kid Rock
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"I love Trump. How can you not love Trump?" – Willie Robertson
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"OK so, I think I'm ready to admit that I'm going to vote for Donald Trump" – Azealia Banks. (She later changed her mind.
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After Trump won, she said he should “stop snorting coke and wearing spray tan.”
"I know him personally. I know him professionally. He's a great guy. He's sharp. He's fast. He can change the country after the last eight years" – Gary Busey
NBC
“Trump has sold me -- what more can I say? ... I just think he’s the only one who’s going to turn this country around.” –Loretta Lynn
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"Of course I'm going to vote for Donald Trump. I think he's amazing. I think he'll make a great president" – Teresa Giudice
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"I only want @realDonaldTrump to win so to smite some of my enemies, kill the politically correct, and basically make America great again!" – Tila Tequila
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"I think he's fantastic. I love him. I think he'd make a great president. He's not a politician, and he doesn't care what anybody thinks" – Stephen Baldwin
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“He should be president of the United States ... Let’s try something new. Let’s run America like a business, where no colors matter. Whoever can do the job, gets the job ... I like Trump" -- Mike Tyson
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"This may be what the country needs and Trump ... he’s a guy who won’t put up with B.S. and has what it takes to change how government is run" – Terrell Owens
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"I’ve always wanted to see the person that’s like, ‘Yeah, I’ve made these comments, these are my beliefs, and you know what, if you don’t like it, stick it. I’m not apologizing, I’m not changing ... Donald Trump is that guy" – John Rocker
CBS
"One thing you know about me is, good or bad, I will always tell it like it is. This guy is the Real Deal, and will Make America Great Again" – Jesse James
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“I love Donald, and he would make a great president ... Number one, he tells the truth. Number two, he’s been where most of these guys want to be, in terms of riding on his own plane." – Wayne Newton
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"Does Donald do everything right? No. The people that hate him, hate him, but people like him because he says things that resonate with what they think ... If I were to vote tomorrow, I'd probably vote for Trump" – Mike Ditka
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"I think he's going to win ... Yes, of course I'm going to vote for him. He's going to run the country as a business. He's going to negotiate. And he knows how to make decisions" – Ivana Trump
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"He is the party. He is the heart and soul of the party” – Ann Coulter
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"[Trump] has been a great friend for many years. We don't need another politician, we need a businessman like Mr. Trump! Trump 2016" – Dennis Rodman
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"I don't want to be in the ring with any candidates, I want to be Trump's running mate." – Hulk Hogan
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"I wish Donald the best. He's a fabulous guy. I hope he goes all the way ... Donald, all he cares about is our country and keeping our country safe. That's what it comes down to" – Lou Ferrigno
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“John Wayne would be very proud of you right now, I think." – Aissa Wayne (The Duke's daughter)
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"Donald Trump should be given the Medal of Freedom for speaking his mind in such a bold, honest and straight-forward manner" – Ted Nugent
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“He speaks like I speak, he communicates with people very well ... We need somebody to relentlessly, relentlessly attack Hillary. It’s the only way we’re going to win. I’m trying to be a classy guy, but to win elections nowadays, the Democrats and liberals attack viciously” – Scott Baio
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"HELLO BOYS! this is my formal endorsement of @realDonaldTrump & I'm a woman!" – Kirstie Alley (She later changed her mind and decided not to endorse anyone.)
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After Trump's win, Alley posted: "CONGRATULATIONS PRESIDENT TRUMP! @realDonaldTrump against all odds ..against the establishment and even against most from the GOP..U did it!"
“Does America want to have a president who FOLLOWS or someone who leads? I vote For @realdonaldtrump” – Aaron Carter. (He later changed his mind.)
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"I'm here" -- former New York Yankee star Paul O'Neill
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"On my way to the @realDonaldTrump rally. Let's make America great again!!!" -- Buffalo Bills guard Ritchie Incognito
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“Everyone is calling him a racist. He just wants people to come into this country legally and fill out the proper paperwork. That’s how I’m viewing it” -- former Yankee outfielder Johnny Damon
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"Having secure borders, protecting our citizens — none of this is hateful. This is the responsibility of the government, and it's the right thing to do. Donald Trump will get it done and put us back on the right track." -- Antonio Sabato Jr.
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“Every critic, every detractor, will have to bow down to President Trump” -- Omarosa Manigault
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"We are moving in, Mr. Trump... If you need anyone to take out the squatters, got your back, Bronx style. #Trump2016" -- Stacey Dash
Twitter/@REALStaceyDash
““What you see is what you get. He has no filter... I knew him before Celebrity Apprentice, privately in clubs and in social situations. He’s the same guy. Some people like it, some people don’t. But he is the same guy. I’m not going to say if I think that’s good or bad” -- Gene Simmons
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“And we need a Donald Trump, and I only know one, so that’s the only son of a bitch we know is Donald Trump.” -- coach Bobby Knight
"And let's be honest folks, we need somebody who believes in this country, we need somebody who's proud of this country and who will fight for this country." -- UFC president Dana White
"If I could only tell you one thing about him, it's that he's probably the hardest working individual I've ever met." -- golfer Natalie Gulbis
"I shocked my staff today ... I said, 'You know what? As far as the Republicans are concerned, I hope Trump wins on the Republican side" – Jesse Ventura. (Though he wanted Trump to be nominated, he supports Libertarian Gary Johnson in the general election.)
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If you enjoyed this list, check out these 167 Hollywood Stars Who Supported Hillary Clinton...
...and this rundown of 5 Hollywood Stars Who Dumped Trump.

1 of 41

These stars backed the president-elect long before he won the election

Hillary Clinton had far more celebrity supporters than Donald Trump, but his 37 celebrity fans turned out to be the ones who backed the winning candidate. Here are Trump's celebrity fans.

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