Two witnesses reportedly submitted texts to the FBI. In addition, the prosecutors have also asked the court to reconsider Manafort's house arrest and send him to jail in light of the new accusations, according to the newspaper.
The special counsel is also probing allegations that Russia interfered in the 2016 US presidential election, as well as accusations that Trump's campaign team colluded with Moscow to affect the outcome of the vote.
Russian officials have repeatedly denied allegations of interference, calling the accusations absurd. Trump has also denied any collusion between himself and the Kremlin and has called Mueller's investigation a witch hunt.