Paul Manafort is not the only subject of the Russia investigation to have been tweaked by the expansion of Robert Mueller’s mandate, which was revealed in court documents earlier this week. (“I don’t really understand what is left of your case,” a U.S. District Court Judge told Manafort’s lawyer on Wednesday, after the government revealed the existence of a memo empowering the special counsel to investigate both whether Manafort colluded with Russia during the 2016 presidential race, and his business activities in Ukraine pre-dating the campaign.) Indeed, the impact of the Mueller probe appears to be growing increasingly international in its scope. On Tuesday, a former London-based lawyer became the first person ensnared in Mueller’s web to be sentenced to prison. The following night, a new report revealed that Mueller has also begun questioning Russian oligarchs, ostensibly to determine whether Kremlin-linked money found its way into Trump campaign coffers during the 2016 election, or the president’s inaugural committee.

Mueller’s team has stopped two Russian oligarchs who recently made trips to the United States, searching at least one, and has made an informal overture to a third requesting an interview and documents, CNN reported Wednesday. According to multiple sources familiar with Mueller’s tactics, the special counsel is focused on the potential flow of money from Russia to Trump’s campaign and inauguration. He’s particularly interested in Russian investments in think tanks and political-action committees that donated to Trump’s campaign, and in “straw donors,” or American citizens who fielded Russian money to skirt campaign finance laws. (American Trump donors with links to Russia have similarly come under scrutiny, CNN reports.)

One of the oligarchs reportedly had his electronic devices searched upon arrival via private jet at a New York-area airport. The stop-and-frisk tactic is designed to catch subjects off guard, robbing them of the chance to wipe their devices, and seems to be a favorite of Mueller’s: former Trump foreign-policy adviser George Papadopoulos, and George Nader—an adviser to Emirati Crown Prince Mohammed bin Zayed Al-Nahyan who attended a secret Seychelles meeting between Blackwater founder Erik Prince and a Russian investor days before the inauguration—were both stopped at Dulles International Airport by the F.B.I., and both are currently cooperating with the Mueller investigation. Ted Malloch, an informal adviser to the Trump campaign, was also stopped by F.B.I. agents in Boston after returning from a trip abroad last month, and is scheduled to appear before a grand jury in April.

That Mueller’s team is shaking down Russians in airports is the latest revelation pointing to the special counsel’s particular interest in the Trump campaign’s foreign ties. Rather than go through Rick Gates to get to Paul Manafort, a report last month indicated that Mueller is much more interested in what Gates has to say about the campaign’s links to Russia—a topic on which, a source told CNN, Gates could be especially helpful. “Was he in the strategy meetings? No. But he was an implementer,” the person said, adding that if there was any coordination between the campaign and Russia, “He would be the kind of person who would probably know that.” Mueller is also reportedly digging into the president’s Russian business ties, including the failed Trump Tower Russia project and the 2013 Miss Universe pageant, searching for signs that Kremlin-linked individuals may have held leverage over him.