(RNN) - Former Trump campaign chair Paul Manafort is set to turn himself in Monday on charges related to the investigation into possible collusion between the campaign and the Russian government.
Manafort was seen entering the FBI field office in Washington, DC, around 8:15 a.m. ET.
CNN and The New York Times reported Manafort would surrender to federal authorities, based on unnamed sources. New York Times also reported Rick Gates, a business partner of Manafort, had been charged.
CNN reported that sealed indictments had come Friday for criminal charges approved by a federal grand jury, the first to come from the probe into Russian meddling in the presidential election. Robert Mueller, the former FBI director, has headed the investigation since being appointed as special counsel in May.
The charges have not been publicly revealed. Mueller's investigation has wide latitude in what it can investigate, so the charges may not be directly related to any campaign action.
The FBI performed a no-knock raid of Manafort's Alexandria, VA, home in August.
U.S. investigators also wiretapped Manafort in 2014, before he became a part of President Donald Trump's campaign, CNN reported. It was authorized under secret court orders, and it continued until early this year, after president Donald Trump was in the White House.
Sources said the FBI investigation initially centered on work done by Washington consulting firms working for Ukraine's former ruling party. A second warrant was part of FBI efforts to investigate suspected ties between Trump campaign associates and possible Russian operatives.
The special counsel was appointed after Attorney General Jeff Sessions recused himself from the Russia investigation and after the president fired former FBI Director James Comey. Mueller impaneled a grand jury in August.