Washington(CNN) Prosecutors Ryan Dickey and Brian Richardson are no longer working for the office of special counsel Robert Mueller, the Justice Department confirmed.

Both lawyers were relatively junior but frequently spotted members of Mueller's corps. Both have worked on court cases that Mueller opened as part of his investigation into Russian interference and coordination with the Trump campaign in the 2016 presidential election.

Peter Carr, a spokesman for the special counsel, declined to explain on Thursday what the departures mean for the state of Mueller's office.

Over this summer, as Mueller opened more criminal cases, other Justice Department units including the US Attorney's Office in Washington and the National Security Division have begun to work on the court action, wedging the cases deeper into the Justice Department's portfolio.

Carr said that neither Dickey nor Richardson left the office because of political allegations, the appearance of bias or any other wrongdoing.

That signals that their departures appear to differ from the situation of Peter Strzok, a top FBI agent moved off of Mueller's team after it was discovered he sent text messages that disparaged President Donald Trump and commented on the firing of FBI Director James Comey.

Trump, in his ongoing attacks of Mueller on Twitter, has repeatedly called the lawyers in the office "17 angry Democrats." Mueller himself is a longtime Republican previously appointed by presidents of both parties to various federal posts, including FBI director days before September 11, 2001.

The special counsel's office now has 15 lawyers at work under Mueller.

Richardson had been among Mueller's attorneys at Dutch lawyer Alex Van Der Zwaan's sentencing in April. Richardson had joined Mueller's office directly -- whereas some lawyers moved over on detail from other parts of the Justice Department -- after he finished a clerkship for Supreme Court Justice Stephen Breyer.

Van Der Zwaan pleaded guilty earlier this year to lying to investigators about his interactions with former Trump campaign leaders Rick Gates and Paul Manafort. Van Der Zwaan went to prison for about a month, then left the US.

Richardson recently became a research fellow at Columbia Law School, according to the law school's spokeswoman Nancy Goldfarb.

Dickey will continue to work on criminal matters at the Justice Department. Though he worked out of Mueller's office last year, he was always employed by the Justice Department's criminal division, specializing in computer and intellectual property crimes.

He has not officially removed himself in court from the legal teams prosecuting three ongoing Mueller-initiated cases. The cases involving Dickey are the indictment of 12 Russian military agents for allegedly hacking Democrats during the election, 16 Russians and companies accused of operating a social media troll farm to influence American voters and the plea deal of a California-based online bank account auctioneer who admitted to identity fraud that helped the Russian social media trolls. That online auctioneer, Richard Pinedo, is scheduled to be sentenced on October 1.

Both Dickey and Richardson were frequent presences at the federal courthouse in DC over the past year, often showing up on days when no public hearings were scheduled even after the court cases they worked on became public. Both appear to have left Mueller's office sometime this summer, though Carr would not confirm their engagement dates.