The F.B.I. said David W. Archey, the lead F.B.I. agent in the special counsel’s office, left the special counsel’s team this month, a signal that the office’s investigative work has come to a close.

Mr. Archey moved to the F.B.I.’s Richmond, Va., field office on March 4 to become the special agent in charge, the bureau said in a news release.

The departures, which NPR first reported, have been closely scrutinized for clues about what they say about the apparent conclusion of the special counsel’s work. The inquiry’s findings seem sure to send shock waves through Washington, whether or not prosecutors found that President Trump or any member of his inner circle worked with Russia to interfere in the election or obstruct the investigation.

Already the investigation — and speculation about when it will end and what its findings will reveal — has consumed the city, and is the focus of cable news reports, book deals and conversations at bars, restaurants and parties.

Mr. Weissmann’s departure also comes as his cases against Mr. Manafort and Mr. Gates are drawing to a close. Mr. Manafort was sentenced on Wednesday in the second of two cases brought against him, and faces a total of up to seven and a half years in prison. (More charges against Mr. Manafort were filed Thursday by the Manhattan district attorney; Mr. Weissmann is not involved in that case.)