WASHINGTON ― Former Trump campaign chairman Paul Manafort and onetime business associate Rick Gates were indicted by a federal grand jury on charges of conspiracy and money laundering in connection with an intensifying investigation into Russian meddling in the 2016 presidential election.

Manafort left his Virginia condo and, with his attorney, walked into the FBI field office in Washington early Monday. A 12-count federal grand jury indictment unsealed shortly after his surrender includes charges of conspiracy against the U.S., conspiracy to launder money, failure to file foreign bank reports and false statements.

Manafort and Gates both pleaded not guilty to the charges in federal court.

Separately, a former Trump campaign foreign policy adviser has pleaded guilty to lying to FBI agents about Russian “dirt” he was offered on Hillary Clinton, according to a plea deal prosecutors unsealed Monday. George Papadopoulos, 30, pleaded guilty on Oct. 5 and has been cooperating in the Russia probe.

The charges are the first in the probe led by the office of special counsel Robert Mueller, a former FBI director. Monday’s arrests come three days after news broke that a federal grand jury in Washington had filed charges stemming from Mueller’s investigation.

“Manafort and Gates generated tens of millions of dollars in income as a result of their Ukraine work,” the indictment says. “In order to hide Ukraine payments from United States authorities, from approximately 2006 through at least 2016, Manafort and Gates laundered the money through scores of United States and foreign corporations, partnerships, and bank accounts.”

Failing to pay taxes allowed Manafort a “lavish lifestyle in the United States,” according to the indictment, which alleges he “spent millions of dollars on luxury goods and services for himself and his extended family through payments wired from offshore nominee accounts to United States vendors.”

Manafort laundered more than $18 million, which he used to buy property, goods and services in the U.S., the indictment alleges. He’s accused of spending $849,215 at one clothing store, $520,440 at another clothing store, about $934,000 at an antique rug store, $62,750 for a Mercedes Benz, and $47,000 for a Range Rover.

Reports have suggested federal investigators could use criminal charges as way to pressure those arrested into providing more information about alleged collusion between President Donald Trump’s campaign and the Kremlin to influence the election. The indictment charging Manafort and Gates makes no mention of Trump or the election.

Jonathan Ernst / Reuters Paul Manafort hides behind his car visor as he leaves his home in Alexandria, Virginia, on Monday.

Trump has aggressively denied allegations that his team colluded with Russia to win the election.

A former prosecutor and FBI director, Mueller partnered with New York Attorney General Eric Schneiderman in August to look into Manafort’s possible financial crimes, including money laundering.

Manafort ran Trump’s presidential campaign from June 2016 until his resignation in August of that year, after reports surfaced about his past lobbying work for pro-Russian Ukrainian oligarchs. He retroactively registered as a foreign agent and disclosed more than $17 million in payments for his firm’s consulting work in Ukraine, which occurred before he joined Trump’s campaign.

“You can get rid of Manafort,” said Robby Mook, who was the campaign manager for Democratic nominee Hillary Clinton, “but that doesn’t end the odd bromance Trump has with [the Russian President].”

Elsa via Getty Images

Manafort met with Senate Intelligence Committee investigators in July to discuss a meeting between Trump associates and a Russian lawyer that was held during the election campaign to obtain dirt on Clinton. The next day, FBI agents seized documents and other items from Manafort’s house in Virginia without warning.

Investigators have also issued subpoenas seeking testimony from a number of people linked to Manafort throughout the probe.

Trump described the pre-dawn raid of Manafort’s home as “pretty tough stuff.”

“I’ve always found Paul Manafort to be a very decent man,” the president said at the time. “He’s like a lot of other people, probably makes consultant fees from all over the place, who knows, I don’t know, but I thought it was pretty tough stuff to wake him up, perhaps his family was there.”

Trump fired FBI director James Comey, who was leading the agency’s investigation into Russian interference in the election, in May. The following week, the Justice Department appointed Mueller as special counsel to oversee the federal inquiry into the Trump campaign’s alleged Russian ties.

“Led by some very bad and conflicted people,” Trump tweeted in June, the Russia probe is “the single greatest WITCH HUNT in American political history.”

This article has been updated to include not guilty pleas by Manafort and Gates.