Two Soviet-born associates of Trump attorney Rudi Giuliani have been arrested on campaign finance violations in an alleged scheme to hide a $325,000 donation to President Trump’s primary super PAC, America First Action.

Lev Parnas and Igor Fruman were arrested Wednesday at Dulles International Airport where they were preparing to board a flight to Frankfort, Germany, U.S. Attorney Geoffrey Berman said. They appeared in federal court in Virginia Thursday and were expected to be transferred to New York. Giuliani said Thursday the pair were traveling to Vienna, Austria, for business reasons.

The two reportedly helped Giuliani in his effort to investigate former Vice President Joe Biden, a leading contender for the 2020 Democratic presidential nomination.

The two Florida businessmen are accused of conspiracy and making false statements to the Federal Election Commission. Two others also were charged in the scheme -- David Correia and Andrey Kukushkin -- to use an LLC to hide the contribution to the pro-Trump PAC. Kukushkin was arrested Wednesday in Los Angeles while Correia remained at large.

Parnas and Fruman dined with Trump in early May 2018, a since-deleted Facebook post showed, the Wall Street Journal reported. They also reportedly met with Donald Trump Jr. at a fundraising breakfast in Beverly Hills, California, a month later.

Parnas and Fruman also donated money to Florida Sen. Rick Scott, the National Republican Congressional Committee and House Minority Leader Kevin McCarthy.

The pair allegedly introduced Giuliani to a number of current and former Ukrainian prosecutors to discuss the Biden case, and Parnas also accompanied Giuliani to a breakfast meeting with Kurt Volker, who resigned last week as the U.S. special representative for Ukraine negotiations.

John Dowd, who previously headed Trump’s legal team and now represents Parnas and Fruman, said his clients would not cooperate with the House Trump impeachment inquiry, which is seeking documents and has schedule the pair for depositions.

Parnas also worked to get former U.S. Ambassador to Ukraine Marie Yovanovitch removed from her post, accusing her of bad-mouthing Trump. He enlisted the help of then-Rep. Pete Sessions, R-Texas, in the effort, who wrote a letter asking why the administration had not replaced her.

Parnas allegedly enlisted the Ukraine-born Fruman’s help in hooking up Giuliani with Ukrainian officials. Giuliani has been pushing the Ukrainians to investigate Biden and his son Hunter for alleged corruption related to the Burisma natural gas company. Hunter Biden had a seat on the company’s board.

Giuliani also wants the Ukrainians to find evidence the hacking of emails involving Hillary Clinton’s presidential campaign and the Democratic National Committee emanated from Ukraine rather than Russia.

The House impeachment investigation was spurred by the administration handling of a whistleblower complaint about a July 25 phone call Trump made to Ukraine President Volodymyr Zelensky in which Trump asked for a “favor,” this just days after Trump froze nearly $400 million in military aid to the country.