A federal grand jury approved the first charges filed by special counsel Robert Mueller, according to an exclusive CNN report. It prevents the target of an indictment from knowing they're about to be charged and arrested, which limits the risk of defendants destroying evidence or any shenanigans when they are eventually brought in.
One day before, Manafort had met with Senate Intelligence Committee investigators to discuss a meeting between a Russian lawyer and members of Trump's campaign team that took place during the 2016 presidential election.
By June, Trump himself was reportedly under investigation for obstruction of justice.
The president has repeatedly denied potential collusion as "fake news" and a "hoax" perpetuated by Democrats.
The investigation is also looking into allegations that Trump obstructed justice when he fired Comey.
Mueller's broad mandate gives him not only oversight of the Russian Federation probe, but also "any matters that arose or may arise directly from the investigation".
Mr Mueller's team has interviewed former White House chief of staff Reince Priebus, former spokesman Sean Spicer and other current and former White House officials as part of the investigation. It is not yet known what charges were filed, or who they were filed against.
Comey said during congressional testimony in June that he felt the president tried to pressure him into dropping the FBI's investigation into former National Security Advisor Michael Flynn four months earlier.