WASHINGTON — Former Trump campaign chairman Paul Manafort and his former business partner Rick Gates will turn themselves in on charges stemming from Special Counsel Robert S. Mueller III’s investigation into possible coordination between the Trump campaign and Russia to influence the 2016 election, according to a person familiar with the matter.

The precise charges the men face were not immediately clear. Gates did not respond to a request for comment, nor did Jason Maloni, a spokesman for Manafort.

Washington – especially those in political and media circles – had been anxiously anticipating the charges since CNN reported Friday night that a grand jury had approved the first charges in Mueller’s investigation. That report was soon matched by others, including Reuters and the Wall Street Journal, though affiliates of many involved said they were in the dark as to what was about to come. About a dozen reporters staked out the entrance to the federal courthouse in downtown D.C. Monday morning, waiting for any glimpse of prosecutors or possible defendants.

Spokespeople for Mueller and the Justice Department declined to comment over the weekend. They did not immediately return messages Monday.

Mueller was appointed in May to oversee the probe of possible coordination between the Trump campaign and Russia, taking over work that the FBI had begun in July 2016. The probe has focused acutely on former Manafort and former national security adviser Michael Flynn, though investigators have shown interest in a broad array of other topics.

Those include meetings the president’s son-in-law, Jared Kushner, had with the Russian ambassador and a banker from Moscow in December, and a June 2016 meeting at Trump tower involving the president’s son, Donald Jr., and a Russian lawyer. Mueller’s team has requested extensive records from the White House, covering areas including the president’s private discussions about firing James Comey as FBI director and his response to news that Flynn was under investigation, according to two people briefed on the requests.

Mueller is also investigating whether Trump obstructed justice leading up to Comey’s firing. His team has been actively presenting records and bringing witnesses before the grand jury in D.C. for the last three months.

Any grand jury indictment would be shared with deputy attorney general Rod Rosenstein, who is acting as the attorney general because Jeff Sessions, having served as a surrogate for the Trump campaign, recused himself from the matter.

Late Friday afternoon, the federal court’s chief judge, Beryl A. Howell, presided as host for a ceremonial portrait unveiling of a fellow judge and explained to the crowd of hundreds of guests that Rosenstein could not be present because of an important meeting he was called to at the Justice Department.

One area of particular focus for the special counsel appears to be the personal finances of Manafort. FBI agents working for Mueller raided Manafort’s home in Alexandria, Virginia, in late July, armed with a search warrant that allowed them to enter at dawn without warning the occupants. Such an invasive search is only allowed after prosecutors have persuaded a federal judge that they have evidence of a crime and they have reasonable concern that key evidence could be destroyed or withheld.

Prosecutors also warned Manafort they planned to indict him, according to two people familiar with the exchange.

A lawyer for Manafort, Kevin Downing, did not respond to requests for comment. However, other Manafort associates said Friday evening they had no indication that Manafort has been or would be indicted.

Flynn’s lawyer, Robert Kelner, said late Friday, “we are not commenting tonight.” A person familiar with Flynn’s defense said he, too, had received no notice of pending indictment.

Wayne Holland, a McEnearney Associates real estate agent who helped Manafort buy the condo in Alexandria that was raided by the FBI this summer, testified Oct. 20 before the grand jury in Mueller’s probe after he and his firm were unsuccessful in an effort to quash subpoenas, Holland said Friday.

Holland declined to discuss his testimony, first reported by Politico, but confirmed that an opinion unsealed Friday by Howell denied his and his firm’s motion to quash a subpoena by claiming real estate broker records are confidential under Virginia and District of Columbia laws.