Former Trump campaign chairman Paul Manafort has been ordered to turn himself in to the FBI as part of the first indictment from special counsel Robert Mueller's probe.

The New York Times reports that Manafort and former business associate Rick Gates are being hit with federal charges as a result of Mueller's probe.

CNN is reporting that Manafort has agreed to turn himself in on Monday. Manafort was spotted leaving his home by Washington, D.C. local news station WUSA 9 being driven by his attorney.

The specific charges being leveled against Manafort and Gates have not been officially announced at this point, although the Times notes that Manafort "had been under investigation for violations of federal tax law, money laundering and whether he appropriately disclosed his foreign lobbying."

The Wall Street Journal, meanwhile, is reporting that Manafort will be charged with tax fraud, among other charges.

Manafort ran Trump's presidential campaign for several months in 2016, before being dismissed in the wake of damaging revelations about his work on behalf of a Kremlin-backed political party in Ukraine. Specifically, the Associated Press reported last year that Manafort helped the party "secretly route at least $2.2 million in payments to two prominent Washington lobbying firms in 2012, and did so in a way that effectively obscured the foreign political party’s efforts to influence U.S. policy."

Additionally, a secret memo that leaked last year revealed that Ukrainian authorities had accused Manafort of organizing protests against a NATO military exercise in Ukraine on behalf of the pro-Russian Party of Regions. One American soldier who was in Ukraine at the time revealed that protesters organized by Manafort threw rocks at NATO troops en route to the training exercise.

Read more here about the 12 counts on which Manafort and Gates were charged, including conspiracy against the United States.