FBI and special counsel investigation
Main article: Special Counsel investigation (2017–present)
The FBI reportedly began a criminal investigation into Manafort in 2014, shortly after Yanukovich was deposed. That investigation predated the 2016 election by several years and is ongoing. In addition, Manafort is also a person of interest in the FBI counterintelligence probe looking into the Russian government's interference in the 2016 presidential election.
On January 19, 2017, the eve of the Trump's presidential inauguration, it was reported that Manafort was under active investigation by multiple federal agencies including the Central Intelligence Agency, National Security Agency, Federal Bureau of Investigation (FBI), Director of National Intelligence and the financial crimes unit of the Treasury Department. Investigations were said to be based on intercepted Russian communications as well as financial transactions. It was later confirmed that Manafort was wiretapped by the FBI "before and after the  election ... including a period when Manafort was known to talk to President Donald Trump." The surveillance of Manafort began in 2014, before Donald Trump announced his candidacy for President of United States.
Special Counsel Robert Mueller, who was appointed on May 17, 2017 by the Justice Department to oversee the investigation into Russian interference in the 2016 United States elections and related matters, took over the existing criminal probe involving Manafort. On July 26, 2017, the day after Manafort's United States Senate Select Committee on Intelligence hearing and the morning of his planned hearing before the United States Senate Committee on the Judiciary, FBI agents at Mueller's direction conducted a "no-knock" pre-dawn raid on Manafort's Alexandria, Virginia home, using a search warrant to seize documents and other materials, in regard to the Russian meddling in the 2016 election.