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Last Updated Oct 30, 2017 8:26 AM EDT

President Trump’s former 2016 campaign chairman Paul Manafort and Rick Gates, Manafort’s former business associate, were told to surrender to federal authorities Monday morning in connection with the investigation into Russian meddling in the U.S. presidential election, The New York Times reports.

CBS News spotted Manafort leaving his apartment in Alexandria, Virginia Monday morning with his lawyer and entering the Washington Field Office of the FBI. 

A federal grand jury used by Special Counsel Robert Mueller approved the first charges stemming from the investigation, CBS News reported Friday.

The indictment is currently under seal but is expected to become public as early as Monday. The nature of the charges is not clear, nor is the identity or number of individuals targeted.

Manafort served as campaign chairman of Mr. Trump’s presidential campaign from March until August of last year. The FBI raided his home over the summer, even picking the lock while he was at home asleep.

CBS News’ Jeff Pegues reports that this signals a new phase in the Russia probe and CBS News’ Paula Reid adds that Mueller is trying to make a statement by moving quickly and aggressively. Reid doesn’t expect anyone else to be charged Monday. 

In September, The New York Times reported that federal prosecutors had planned to indict Manafort. CBS News confirmed that month that Manafort had been wiretapped under a foreign intelligence warrant in connection with U.S. concerns that he was communicating with Russian operatives who wanted to influence the American election. The warrants were issued before Robert Mueller was appointed as special counsel to take over the investigation from the FBI.

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