When two business associates of Rudolph W. Giuliani, President Trump’s personal lawyer, were arrested this month on charges that they funneled foreign money into U.S. elections, federal prosecutors working on a different case in Chicago took note.

The investigators had previously come across the two men, Lev Parnas and Igor Fruman, as they pursued a long-standing case against a Ukrainian gas tycoon accused of bribery, according to two people familiar with the matter. They, like others interviewed regarding the case, spoke on the condition of anonymity to discuss the ongoing litigation.

The Chicago prosecutors reached out to their counterparts in New York, where the foreign money charges had been brought, to offer assistance, the people said.

Parnas had been working as an interpreter for the lawyers of the tycoon, Dmytro Firtash, since late July. Chicago prosecutors suspect there might be a broader relationship among Firtash, Parnas and Fruman, the people familiar with the matter said.

The new focus on possible ties among the three men comes as the Ukrainian energy mogul has appeared to align himself with Trump and the president’s allies as he fights extradition to the United States.

This summer, Firtash — at Parnas’s recommendation — hired two conservative attorneys who are top defenders of the president.

Meanwhile, Parnas and Fruman, Soviet-born emigres with deep business ties in Ukraine, had been assisting Giuliani’s hunt for damaging information about Democrats in that country, an effort that is now the focus of the presidential impeachment inquiry.

The Ukrainian energy mogul is now facing questions about whether he has played a shadow role in that effort. The Firtash case has helped provide fodder for Giuliani’s theories through one known avenue: In September, Firtash’s Austrian lawyers filed in court an affidavit by a former Ukrainian prosecutor in which the prosecutor claimed he was fired because he was investigating then-Vice President Joe Biden’s son Hunter Biden. Giuliani has since cited that document as evidence supporting his claims.

Attorneys for Firtash denied that the energy mogul has any kind of business relationship with Parnas and Fruman. And a member of his legal team said Firtash played “no role whatsoever” in Giuliani’s efforts, adding: “His whole focus has been on his legal case.”

Firtash, who federal prosecutors have alleged has ties to Russian organized crime, has remained a powerful figure in Ukraine despite living in exile in Austria. He denies ties to organized crime and any wrongdoing in the Chicago case.

In July, the tycoon changed legal teams, replacing longtime Democratic lawyer Lanny Davis with the husband-and-wife team of Victoria Toensing and Joseph diGenova, who appear frequently on Fox News to defend Trump and have served as informal advisers to Trump’s legal team, including Giuliani.

After taking on Firtash’s case, Toensing and diGenova secured a rare face-to-face meeting with Attorney General William P. Barr and other Justice Department officials to argue against the charges, three people familiar with the meeting said.

Barr declined to intercede, the people said.

A Justice Department spokeswoman said that the case “has the support of the department leadership,” adding: “We continue to work closely with the Austrian Ministry of Justice to extradite Mr. Firtash.”

Toensing declined to comment on the Barr meeting.

Spokesmen for the U.S. attorney’s offices in Chicago and Manhattan declined to comment on their investigations.

In a statement, a spokesman for Toensing and diGenova said that Firtash first met Parnas in June and that Firtash has “no business relationship” with either Parnas or Fruman. “No money has been paid to Mr. Parnas by Mr. Firtash beyond his work as a translator for the law firm,” the spokesman said.

In an interview last week, Giuliani called Firtash an “interesting” guy but said he never met him or worked on his behalf.

“I did sort of look at Firtash to see if he had any relevant information,” to assist his claims, Giuliani said. “As far as I can tell, he didn’t. I looked at maybe 20 of these oligarchs.”

He said he did not know whether Firtash had a relationship with Parnas and Fruman. “It’s none of my business,” Giuliani said.

Lawyers for Parnas and Fruman declined to comment.

Fighting extradition

Earlier this year, Giuliani expressed disdain for Firtash, asserting that the wealthy Ukrainian had ties to the Russian mob. At the time, Firtash was still represented by Davis, who was also acting a lawyer for Trump’s former attorney Michael Cohen, making him a top target for Trump’s ire.

Davis is being paid by “this guy who’s considered to be one of the high-level Russian organized crime members or associates,” Giuliani told the Hill newspaper in March.

Firtash made his fortune through his ownership of a middleman company that sold natural gas from a Russian state-owned company to Ukraine’s state-owned natural gas supplier and from the Ukrainian company to consumers. The job required connections in both Kyiv and Moscow. He has also invested in a network of factories and other companies, adding to his power through his employment of thousands of Ukrainians.

In a 2017 court filing, U.S. federal prosecutors alleged that Firtash had ties to the “upper echelons” of Russian organized crime. The gas tycoon has been linked in a U.S. diplomatic cable to Semion Mogilevich, a Ukrainian indicted in Pennsylvania in 2003 on more than 40 counts of racketeering, fraud and money laundering and now living in Moscow.

The FBI has alleged that Mogilevich, nicknamed the “boss of bosses,” is also involved with “weapons trafficking, contract murders, extortion, drug trafficking, and prostitution on an international scale.”

In 2010, WikiLeaks published an internal U.S. diplomatic cable from years earlier in which then-U.S. Ambassador to Ukraine William B. Taylor Jr. wrote that Firtash had “acknowledged ties” to Mogilevich in a private meeting. Taylor wrote that Firtash had denied breaking the law but said “he needed Mogilevich’s approval to get into business in the first place.”

A member of the Firtash legal team said Taylor’s description of the conversation is false.

Firtash has since insisted he has no ties to Russian organized crime, telling Time magazine in 2017 that he was never Mogilevich’s partner. “He’s Ukrainian. . . . Half the country knows him. So what?” Firtash said then. “Knowing him doesn’t mean answering for him.”

Firtash was charged in Chicago in 2013, accused of bribing Indian officials related to mining interests in that country. He was arrested in Austria the following year at the request of American officials, but released on $172 million bond and has been living in Vienna ever since while he has fought extradition.

In June, the Austrian Supreme Court ruled against Firtash, paving the way for his removal to the United States.

At that point, Firtash tried one last-ditch effort to forestall the long-delayed start of his U.S. trial.

That month, the energy mogul met Parnas in Vienna through a mutual Ukrainian friend, according to a person familiar with the episode. At the time, Firtash was considering switching lawyers and asked about Toensing and diGenova. Parnas vouched for the couple, whom he had met through Guiliani, and urged Firtash to hire them, the person said.

Toensing and diGenova, in turn, brought Parnas aboard as an interpreter the following month, according to Toensing, who said she was impressed by him his language skills and knowledge of the region.

On July 23, Davis, who had been registered as a foreign agent to represent Firtash, filed paperwork indicating that he was no longer working for the Ukrainian. In a statement, he said he had been replaced by Toensing and diGenova.

Unlike Davis, they have not registered with the Justice Department as foreign agents. A spokesman for diGenova and Toensing’s law firm said that their representation of Firtash falls under a part of the foreign agents law that specifically exempts legal services from the registration requirement.

In recent months, Firtash’s Austrian lawyers filed a court document criticizing the Justice Department in ways that echo Trump’s own attacks on the department, according to a person familiar with the sealed Austrian proceedings.

The attorneys argued that the case against Firtash was politically motivated because Andrew Weissmann, a lawyer working for then-special counsel Robert S. Mueller III, had offered to resolve Firtash’s case if he would implicate Trump and former campaign chairman Paul Manafort in Russian interference in the 2016 election.

In its response, the Justice Department noted the investigation into Firtash began more than a decade ago and that he was charged in 2013 — long before there was a special counsel’s office or Trump was even a presidential candidate — and thus could not be politically motivated, according to a person familiar with the matter. The department also disputed that Weissmann had told Firtash’s team he could have the case dropped, the person said.

In response, an Austrian court has now reopened Firtash’s case, putting his extradition on hold again.

Business and politics

In 2018, Parnas and Fruman began a steep ascent into an inner circle of Trump backers, dining at the White House with Trump and breakfasting in California with his son Donald Trump Jr. Giuliani regularly took the two men to official and unofficial events, including political gatherings, sporting events and the December 2018 funeral of former president George H.W. Bush.

The former New York mayor even invited the two men this year to an annual commemoration he organizes of the Sept. 11 terrorist attacks, people familiar with the event said, leaving Giuliani’s longtime colleagues in New York government scratching their heads.

At the same time, Parnas and Fruman began touting their close ties to Giuliani as they pursued their own business interests.

They also invoked Firtash’s name as they sought business for a new liquefied natural gas company that they had founded in 2018, according to two people familiar with the conversations.

At an energy conference in Houston in March, the two made a pitch to Ukrainian state oil and gas giant Naftogaz, approaching a top official at the company, Andrew Favorov, according to a colleague of Favorov.

During a series of meetings, Parnas and Fruman proposed selling gas to the company, said Dale W. Perry, a former Favorov partner whom the Ukrainian briefed shortly after the meetings.

Parnas and Fruman told Favorov that they hoped to see new leadership at Naftogaz soon that would be receptive to their proposal and the ouster of then-U.S. Ambassador to Ukraine Marie Yovanovitch, whom they perceived as opposed to their plans. By May, she had been removed from her post on Trump’s orders.

In an interview, Perry said Parnas and Fruman’s grand plan included one other element that Favorov found puzzling at the time: They said Naftogaz should put aside financial disputes with Firtash, a decision that could provide a windfall of more than $1 billion for the tycoon.

“He was like, ‘The Firtash debt? Why are these guys talking about that?’ ” Perry said of Favorov. “He just couldn’t understand it.”

Favorov could not be reached for comment.

Meanwhile, Parnas and Fruman were also assisting Giuliani as he sought information in Ukraine to prove his claims that Democrats received help from Ukrainians during the 2016 election and that Biden had orchestrated the 2016 removal of a Ukrainian prosecutor because he was investigating the gas company Burisma, whose board included Biden’s son.

In fact, the international community was broadly in favor of removing the prosecutor, Viktor Shokin, and the Burisma investigation was dormant at the time that Biden urged his removal.

But in January 2019, Parnas and Fruman helped connect Giuliani by Skype to Shokin, who alleged to the former New York mayor that his firing was connected to his Biden work. On Sept. 4, Shokin swore out a 12-page affidavit attesting to that same fact, a document Giuliani has waved on television as proof of his allegations.

According to the document, it was prepared “at the request of lawyers acting for Dmitry Firtash.”

Alice Crites, Paul Sonne, Jeanne Whalen and Carol D. Leonnig contributed to this report.