FBI agents have served a search warrant at one of the homes of Donald Trump's former campaign chairman Paul Manafort, his spokesman said.
Spokesman Jason Maloni said that Mr Manafort cooperated with the agents as he has "consistently" done.
Mr Manafort has been a subject of a long-standing FBI investigation into his dealings in Ukraine and work for the country's former president, Viktor Yanukovych.
Special counsel Robert Mueller is also investigating Mr Manafort as part of his probe into Russia's meddling in the 2016 election and any possible collusion with Trump associates.
Mr Manafort has denied any wrongdoing. He has also cooperated with congressional committees investigating the election interference.
He has turned over documents to the intelligence and judiciary committees in the Senate.
Mr Manafort led the Trump campaign for several months.