FILE PHOTO: Former New York City Mayor Rudy Giuliani speaks during a rally to support a leadership change in Iran outside the U.N. headquarters in New York City Reuters

Federal prosecutors have widened their investigation following the arrest of Rudy Giuliani’s associates Lev Parnas and Igor Fruman, and are seeking information about Giuliani’s lobbying firm, reported The Wall Street Journal.

Parnas and Fruman, who reportedly helped Giuliani in his push for a Ukrainian investigation into Democratic presidential contender Joe Biden, were arrested in October on campaign finance charges.

One investigative source told the Journal that investigators were probing whether Giuliani may have been acting as an „unregistered foreign agent.“

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Federal prosecutors in the Southern District of New York have expanded their investigation following the arrest of two associates of Rudy Giuliani, and are probing the former New York mayor’s consulting firm, The Wall Street Journal reported Monday.

Sources familiar with the matter told the Journal that subpoenas have been issued by federal investigators to potential witnesses as part of the investigation into Igor Fruman and Lev Parnas, two associates of Giuliani arrested in October on charges of illegally channeling foreign money into Republican election campaigns.

Both men deny the charges.

According to the Journal’s report, the subpoenas also sought information about Giuliani, the former New York mayor and personal attorney of President Donald Trump.

One investigative source told the publication that they were probing whether Giuliani violated the law by acting as an unregistered foreign agent, or concealed his work for foreign clients.

Associated Press/Mark Lennihan

One of the focuses of the investigation is Giuliani’s consulting firm, Giuliani and Partners, the report notes. Among the money laundering, obstruction of justice, and campaign finance violations among the potential offences being investigated,

The Washington Post, citing people familiar with the investigation, also reported that Giuliani’s firm is under investigation, and that prosecutors „are casting a wide net for wrongdoing as they examine the business and legal dealings of the president’s personal lawyer,“ and his two associates.

Giuliani told the publication that he had never served as a lobbyist or agent of a foreign government.

He has not been accused by investigators of any wrongdoing.

„I have yet to find anybody that’s actually seen the subpoenas,“ Giuliani’s attorney, Robert Costello, told CNBC.

„I would like to see one, then I could make a reasonable judgment of what is going on,“ Costello said.

Of Giuliani, he said: „I can tell you that he didn’t do anything wrong, and he has no fear of any investigation of what he did.“

FILE PHOTO: Igor Fruman arrives for his arraignment at the United States Courthouse in the Manhattan borough of New York City, U.S., October 23, 2019. REUTERS/Eduardo Munoz/File Photo Reuters

Costello did not immediately respond to a request for additional comment from Business Insider .

Giuliani’s connections with Parnas and Fruman are not entirely clear, but numerous media outlets have reported that Giuliani enlisted the help of the men to broker contacts with Ukrainian officials, as he sought to pressure Ukraine to announce a probe into Joe Biden, a key domestic rival of Trump.

Giuliani was acting as an unofficial emissary for President Trump in seeking the Biden investigation from Ukraine, which has sparked an impeachment probe into the president’s actions.

The arrest of Parnas and Fruman is unrelated to the impeachment inquiry, and relates to alleged campaign finance violations carried out by the men.

It was reported by ABC Sundaythat Parnas handed over secret recordings of Trump and Giuliani to investigators on the House Intelligence Committee as part of the impeachment inquiry into Trump.