Special Counsel Robert Mueller departs St. John's Episcopal Church, across from the White House, after attending morning services, in Washington, Sunday, March 24, 2019.

The federal grand jury that Robert Mueller was using is still working "robustly" even after the special counsel submitted his final report to the Justice Department, a prosecutor said at a court hearing Wednesday.

The revelation means the panel could issue further indictments even as the special counsel's shop closes after two years of work.

The grand jury in January indicted longtime Trump advisor Roger Stone on multiple charges. The U.S. Attorney's Office in Washington is now responsible for prosecuting Stone.

The U.S. Attorney's Office and potentially other Justice Department prosecutors would be handling presentation of evidence to the grand jury and making subpoena requests in any other cases the panel continues to work on.

Wednesday's hearing in Washington before U.S. District Court Chief Judge Beryl Howell dealt with a motion filed by the Reporters Committee for Freedom of the Press.

That journalism advocacy group wants to have unsealed details of a case in which the grand jury, acting at Mueller's request, subpoenaed information last year from an unidentified foreign-owned company.

The press group, which has long sought those details, is arguing there is even less reason for secrecy because Mueller has finished his investigation.

The mysterious foreign-owned company, whose refusal to comply with the subpoena has left it owing contempt-of-court penalties believed to be in excess of $2 million, saw the Supreme Court on Monday reject its request to hear an appeal of lower court rulings upholding the demand for documents.

Howell on Wednesday asked federal prosecutor David Goodhand if the grand jury had finished its investigation.

"No," Goodhand answered. "I can say it's continuing robustly."

Federal grand juries work in secret. Their actions typically come to light only when it issues charges in a case in the form of an indictment.

Peter Carr, spokesman for the special counsel's office, declined to comment. A spokesman for the U.S. Attorney's Office in Washington had no immediate comment.

Mueller, who was investigating Russian interference in the 2016 presidential election and related issues, turned in his final report to Attorney General William Barr on Friday. The final report has not been publicly released.

On Sunday, Barr, in a letter to top members of Congress, said Mueller's probe did not find sufficient evidence to establish that President Donald Trump obstructed justice in connection with the investigation, or that Trump's campaign colluded with Russia to influence the 2016 election.

Barr also said that Mueller had not obtained any new indictments since that of Stone. There had been speculation that the special counsel would obtain sealed indictments from the grand jury that would later be revealed.

Trump claimed the report was a "full exoneration" — but it was not.

Barr, in his letter, directly quoted Mueller as saying that, "while this report does not conclude that the President committed a crime, it also does not exonerate him."

Mueller previously had used the grand jury to bring charges against multiple people connected to Trump, including Stone, former campaign manager Paul Manafort, former national security advisor Michael Flynn, former campaign and inaugural official Rick Gates and the president's former personal lawyer Michael Cohen.

The U.S. Attorney's Office in Washington is now handling remaining work in those and other cases Mueller had lodged.

At Wednesday's hearing, attorneys for the unidentified foreign company told Howell the firm "had no interest" in being identified to the public.

Howell did not make a decision Wednesday on the motion by the Reporters Committee for Freedom of the Press to unseal details about the subpoena, but said she will consider it.