Donald Trump's ex-campaign manager, Paul Manafort, has handed himself into the FBI after reports he will face charges in relation to the investigation into collusion with Russia.
Mr Manafort's associate Rick Hayes has also been brought in for questioning.
The nature of the charges are not yet known, but they are the first people to be arrested as part of special counsel Robert Mueller's investigation into alleged collusion between the Trump campaign and Russia.
Earlier, President Trump had dismissed claims of collusion between his presidential campaign and Russia as a "witch hunt" and "phony".
US intelligence agencies have already concluded that the Russian government attempted to influence the 2016 election in favour of Mr Trump.
The President took to Twitter yesterday to denounce the claims and launch an attack on the Democrats.
He accused the party and his presidential rival Hillary Clinton of a "witch hunt" being used for "evil politics".
..."collusion," which doesn't exist. The Dems are using this terrible (and bad for our country) Witch Hunt for evil politics, but the R's...
— Donald J. Trump (@realDonaldTrump) October 29, 2017
...are now fighting back like never before. There is so much GUILT by Democrats/Clinton, and now the facts are pouring out. DO SOMETHING!
— Donald J. Trump (@realDonaldTrump) October 29, 2017