WASHINGTON — Federal prosecutors in Manhattan issued subpoenas in recent weeks to several players in President Trump’s fund-raising apparatus as part of an investigation into two associates of Rudolph W. Giuliani who have been charged with violating campaign finance laws, according to people familiar with the investigation.
The subpoenas went to a lobbying firm run by a top fund-raiser for Mr. Trump, Brian Ballard, and to two people who have helped raise money for America First Action, a super PAC created to support the president and allied candidates, the people said.
Mr. Ballard and the America First fund-raisers worked to varying extents with Mr. Giuliani’s associates Lev Parnas and Igor Fruman, American citizens who helped Mr. Giuliani wage a pressure campaign on Ukraine that is now at the center of the impeachment inquiry into Mr. Trump.
The recent activity by prosecutors and F.B.I. agents shows that they have cast a wide net as they collect evidence about Mr. Parnas and Mr. Fruman, who were arrested last month. It also comes as the same prosecutors look into whether Mr. Giuliani, Mr. Trump’s personal lawyer, violated a federal lobbying law in some of his dealings with Ukrainians.
Mr. Giuliani and one of his companies were mentioned by name in one of the subpoenas, which was issued to a businessman who was approached by Mr. Parnas seeking an investment.
He was trying to finance a portion of a $500,000 payment he had promised to Mr. Giuliani to consult for a company he helped found, Fraud Guarantee, according to a person familiar with the solicitation of the businessman. The businessman never provided the money.
There is no indication that those who have received subpoenas or agreed to provide documents or interviews are suspected of wrongdoing. Prosecutors and F.B.I. agents have been seeking to speak with witnesses about how Mr. Parnas and Mr. Fruman gained entree into elite Republican finance circles that brought them into direct contact with Mr. Trump.
Mr. Parnas and Mr. Fruman were charged with violations related to donations to various Republican politicians and groups, including a $325,000 contribution made to America First Action. They made the donation in the name of a company they had recently founded, Global Energy Producers.
America First Action has voluntarily turned over documents to prosecutors in Manhattan, according to people familiar with the investigation.
Prosecutors also arranged a voluntary interview in New York as soon as this week with Andrew Favorov, an executive with the Ukrainian state-owned gas company Naftogaz whom Mr. Parnas and Mr. Fruman tried to enlist in an effort to win business, potentially through Global Energy Producers.
Mr. Favorov has Russian and United States citizenship, and permanent resident status in Ukraine. His interview, which was first reported by The Associated Press, suggests that prosecutors’ interest in Mr. Parnas and Mr. Fruman extends beyond their political donations, and into their business efforts.
The authorities arrested Mr. Parnas and Mr. Fruman on Oct. 9, sooner than previously planned, fearing they would leave the country without plans to return.
Mr. Parnas and Mr. Fruman, who have pleaded not guilty, played major roles in the effort by Mr. Trump and Mr. Giuliani to pressure the Ukrainian government to commit to investigations that could be politically helpful to Mr. Trump, which was first reported by The New York Times.
Mr. Parnas and Mr. Fruman helped connect Mr. Giuliani to Ukrainian prosecutors who claimed to have incriminating information about former Vice President Joseph R. Biden Jr., a leading contender for the 2020 Democratic presidential nomination. The prosecutor also claimed to have damaging information about Ukrainians who sought to undermine Mr. Trump in 2016 and about Marie L. Yovanovitch, the United States ambassador to Kyiv and a target of Mr. Trump and his allies.
Democrats contend that the efforts to force Ukraine to investigate those targets were an abuse of power. And witnesses in the impeachment hearings have suggested that Mr. Giuliani, Mr. Parnas and Mr. Fruman had financial motivations for pursuing the Ukrainian pressure campaign.
In addition to the investigation by federal prosecutors for possible violations of a lobbying law, Mr. Giuliani has been subpoenaed by the House’s impeachment investigators. He has denied wrongdoing and said that he has no current business interests in Ukraine.
Mr. Giuliani, the former New York City mayor, has acknowledged accepting $500,000 for business and legal advice from Fraud Guarantee, and said that he represented Mr. Parnas and Mr. Fruman on a legal matter in Ukraine.
The investigation into Mr. Giuliani grew out of the investigation into Mr. Parnas and Mr. Fruman. The charges against Mr. Parnas and Mr. Fruman are narrowly focused, and mostly unrelated to the Ukrainian pressure campaign. Mr. Parnas has indicated a willingness to work with congressional impeachment investigators, but it is unclear whether he will testify.
Mr. Giuliani met Mr. Parnas and Mr. Fruman as they became involved in the Republican major-donor circuit, and the recent activity by prosecutors suggest that they are interested in learning more about how the men gained entree into that world.
Mr. Parnas also developed a relationship through Republican donor politics with Mr. Ballard, whose firm, Ballard Partners, paid Mr. Parnas at least $22,500 for referring business from the Turkish government.
William W. Taylor III, a lawyer for Ballard Partners, confirmed that the business referred by Mr. Parnas was with the Turkish government. Mr. Taylor said in a statement: “Ballard Partners is cooperating with a United States attorney’s office for the Southern District of New York investigation. It has received a subpoena and is complying.”
Kelly Sadler, a spokeswoman for America First Action, said in a statement that the group contacted the Southern District of New York last month “and offered to voluntarily cooperate.”
“We have not been issued any subpoenas,” she added. “America First Action strictly follows the law and, as this is an open matter, we have no further comment.”
Joseph A. Bondy, a lawyer for Mr. Parnas, said he and his client were “pleased to know that the U.S. attorney’s office in the Southern District of New York is continuing its investigation, and look forward to its witnesses providing complete and accurate information in response to their questions.”
A spokesman for Geoffrey S. Berman, the United States attorney in Manhattan, declined to comment.
Kenneth P. Vogel reported from Washington, and Michael Rothfeld, Ben Protess and William K. Rashbaum from New York.