CNN  — 

A criminal appellate prosecutor who was part of an ongoing subpoena fight related to the special counsel’s investigation into Russian election interference concluded his detail with the team in December, the special counsel’s office has announced.

The announced departure of Scott Meisler comes amid growing indications the special counsel is winding down the investigation.

Of the 17 prosecutors who joined Mueller’s team within the Justice Department since May 2017, Meisler is the fourth known to have to exited the office.

He is still working for the Justice Department and on cases related to Robert Mueller’s investigation, according to Peter Carr, a spokesman for the unit run by Mueller. Other divisions of the Justice Department have taken on more responsibility in matters launched by Mueller.

“Scott Meisler concluded his detail with the Special Counsel’s Office in December 2018 and returned to the Criminal Division but continues to represent the office on specific pending matters that were assigned to him during his detail,” Carr said on Tuesday.

Acting Attorney General Matthew Whitaker said last week the Mueller investigation was “close to being completed.” Sen. Chuck Grassley, a Republican Judiciary committee member, said earlier Tuesday he expected Mueller’s final report to come out within a month, then corrected his statement later in the day, saying it was based on rumors.

Meisler has continued to work out of the special counsel’s offices sporadically over the past month. He is one of at least two prosecutors from the office who has fought for information from a company wholly owned by a foreign country in recent months. There’s no indication yet they’ve gotten the information they sought, but prosecutors Tuesday night indicated they’re willing to reveal more about the ongoing fight in the court system.

Meisler’s most visible work on the Mueller team – aside from the mystery subpoena case – came when he handled some legal arguments related to Paul Manafort’s criminal case, which is nearing its end as Manafort heads to his sentencing next month.

Meisler is also a key part of the long-running and still-unresolved challenge to a subpoena in the Mueller probe. He and prosecutor Zainab Ahmad fought the case for Mueller against a foreign-government owned company that wanted to dodge turning over information to a grand jury, according to various court records. Ahmad still works with the Special Counsel’s Office.