Special counsel Robert Mueller has referred a “collection of cases” to federal prosecutors in the Southern District of New York that probe whether high-profile lobbyists and operatives failed to register as foreign agents while reportedly doing work for Ukraine, CNN reports. Since the spring, Mueller has reportedly turned over a case concerning Democratic lobbyist Tony Podesta and his former firm, the Podesta Group. He has also turned over matters involving former Rep. Vin Weber, who worked for Mercury Public Affairs, and former Obama White House counsel Greg Craig, an ex-partner at Skadden Arps law firm. The Daily Beast previously reported that a team at Skadden Arps led by Craig “produced a report that whitewashed the pro-Putin government of Viktor Yanukovych for jailing Yanukovych’s anti-Kremlin predecessor.” Former Trump campaign chairman Paul Manafort previously did consulting work for Yanukovych’s political party. It is not clear if the three men are being considered in one case or in separate cases, and none of the individuals or entities in question have been “charged with wrongdoing,” CNN reports. This comes after Mueller turned over matters involving former Trump lawyer Michael Cohen to the SDNY, and as one of Manafort’s trials began Tuesday in Virginia. Manafort has been charged with failing to register as a foreign agent while working on behalf of Ukraine.