US investigators wiretapped former Trump campaign chairman Paul Manafort under secret court orders before and after the 2016 election, CNN reported today.
The New York Times, citing two people close to the case, also reported that prosecutors told Manafort they planned to indict him.
Federal agents had raided Manafort's Virginia house in July.
Manafort is one of several close advisers who helped President Donald Trump win the 2016 election and who are now being investigated as part of Special Counsel Robert Mueller's probe of alleged Russian interference in the US vote.
Manafort became Trump's campaign manager in June 2016 but was forced to resign two months later amid reports of his business relationship with the Kremlin-backed former Ukrainian leader, Viktor Yanukovich.