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WASHINGTON — The special counsel's office has confirmed that Andrew Weissmann, Robert Mueller's top prosecutor, will be leaving his post.

"Andrew Weissmann will be concluding his detail to the Special Counsel's Office in the near future," said Peter Carr, spokesman for the special counsel, in a statement to NBC News.

The news was first reported by National Public Radio, citing two sources familiar with the matter, and was then confirmed to NBC News by a source close to Weissmann, who said he would be leaving in the next week or so.

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Mueller's top FBI investigator, David Archey, has also left Mueller’s team to become the agent in charge of the Richmond field office, according to an FBI announcement posted Friday. A top counterintelligence official, Archey had been the senior agent on Mueller’s team.

The high-profile departures are the latest public sign that the special counsel is close to wrapping up his investigation into possible links between the Trump campaign and the 2016 Russian election interference effort.

Law enforcement and congressional officials have told NBC News that the Mueller investigation is nearing its end. A confidential report by Mueller’s office is expected to be sent to the Department of Justice soon. Congressional Democrats say they will demand its full release.

Weissmann is the former chief of the Justice Department criminal fraud section who led the prosecution of former Enron executives. Previously, as a prosecutor in New York, he tried two dozen mafia cases, according to news reports.

Special counsel Robert Mueller leaves a meeting with members of the Senate Judiciary Committee on June 21, 2017. Alex Wong / Getty Images

Weissmann led the arguments in the sentencing of former Trump campaign chairman Paul Manafort on Wednesday, and many members of the Mueller team were in the courtroom. The source said Weissmann would not be leaving with major unfinished legal business still to play out. There has been no sign that the Mueller grand jury has met since it released an indictment of former Trump associate Roger Stone in January.

Weissmann will resume teaching at New York University, among other engagements, the source said.

Multiple law enforcement officials tell NBC News that Mueller has farmed out cases not directly related to Russia to other Justice Department offices. Prosecutors in New York continue to investigate individuals in the Trump Organization and the Trump inaugural committee, while prosecutors in Virginia investigate foreign lobbying.