Federal investigators are looking into Rudy Giuliani's involvement with two men indicted for campaign finance violations, a person familiar with the matter told CBS News.

The two men, Lev Parnas and Igor Fruman, are associates of Giuliani, who is President Trump's personal attorney. The ongoing criminal investigation will include scrutiny of any business dealings Giuliani may have had with the two men, the person familiar with the matter said.

The investigation into campaign finance violations by Parnas and Fruman, which was opened about a year ago, is being conducted by the FBI in New York and investigators from the Southern District of New York. The two men were arrested at Dulles Airport last week as they were about to board a plane to leave the country. A Justice Department spokesperson declined to comment.

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CNN first reported that Giuliani's financial dealings with Parnas and Fruman were under scrutiny. The New York Times reported Friday that federal prosecutors are investigating whether Giuliani violated foreign lobbying laws in his work in Ukraine.

An attorney for Giuliani, former Watergate prosecutor Jon Sale, told CBS News he had "no comment" on reports of the investigation.

Giuliani told CBS News he has no knowledge of an investigation and has not been interviewed by FBI. He said that if prosecutors are investigating and leaked it to the media, that would be an indication they are "politically motivated."

Parnas and Fruman are accused of conspiring to "circumvent the federal laws against foreign interference by engaging in a scheme to funnel foreign money to candidates for federal and State office," according to a four-count indictment in the Southern District of New York. Two other men, David Correia and Andrey Kukushkin, also face charges.

The charges include conspiracy, falsifying records and making false statements to the Federal Election Commission.

Both men donated to Republican campaigns and gave $325,000 to America First Action, a pro-Trump super PAC in 2018. The indictment accuses them of setting up a phony company to conceal the source of the contributions.

Despite saying on Friday that he was unsure if Giuliani was still his attorney, Mr. Trump tweeted on Saturday that Giuliani was a "great guy and wonderful lawyer."