New York federal prosecutors have launched a criminal investigation into President Trump's personal lawyer Rudy Giuliani to determine if he "broke lobbying laws in his dealings in Ukraine," the New York Times reports.

Driving the news: Two foreign-born Trump donors who helped connect Giuliani with Ukrainian officials in his efforts to investigate former Vice President Joe Biden and his son were arrested on Wednesday night on campaign finance charges.

What's happening: Investigators are reportedly looking at "Giuliani’s efforts to undermine" former U.S. ambassador to Ukraine Marie Yovanovitch, who testified on Friday to 3 House committees that are investigating Trump and Ukraine and said the president pressured a top State Department official to oust her.

Those committees later said they subpoenaed the ambassador after the White House, through the State Department, directed her not to testify.

the ambassador after the White House, through the State Department, directed her not to testify. Trump replaced Yovanovitch in May in part because of former Ukrainian Prosecutor General Yuri Lutsenko's corruption allegations against Biden, according to the whistleblower report that alleges Trump used "the power of his office to solicit interference from a foreign country in the 2020 election."

What he's saying: Giuliani "said that federal prosecutors had no grounds to charge him with foreign lobbying disclosure violations" since he was acting on behalf of Trump and not former Ukrainian Prosecutor General Yuri Lutsenko when he gathered information on Yovanovitch and "relayed it to the American government and the news media," per the Times.

Where it stands: "It was unclear how far the investigation has progressed, and there was no indication that prosecutors in Manhattan have decided to file additional charges in the case," per the Times.

Go deeper: Foreign-born Giuliani associates arrested on campaign finance charges