A federal grand jury being used by the team of Special Counsel Robert Mueller has been extended, Fox News has learned. The original term of 18 months for the Washington, D.C.-based jury expired on Friday.

Sources close to Chief Judge of U.S. District Court in Washington, Beryl Howell, tell Fox News she has extended the grand jury term.

It wasn’t immediately clear if the extension is for another six months.

A grand jury may serve more than 18 months only if the court, having determined that an extension is in the public interest, extends the grand jury's service. An extension may be granted for no more than 6 months, except as otherwise provided by statute.

Mueller, 74, took over the federal government’s probe into alleged collusion between President Trump’s campaign and Russian officials in May 2017. Already, his investigation has led to charges for multiple Trump campaign associates, though none of the charges are directly related to any misconduct by the president's campaign.

Trump has submitted written responses to several questions as part of Mueller’s investigations and has repeatedly denied any “collusion” with Russians.

MUELLER'S RUSSIA INVESTIGATION: WHAT TO KNOW

For the inquiry into the 2016 election, Mueller has the authority to prosecute any crimes uncovered during this investigation, and he was given wide authority to investigate whether Trump or his associates colluded with the Kremlin to win the White House.

Mueller first impaneled a grand jury in the Russia probe in the summer of 2017. The extension of the grand jury's term on Friday seemingly conflicts with recent reports that Mueller could complete his investigation - and submit a report to the attorney general - next month.

Fox News' Jake Gibson and Kaitlyn Schallhorn contributed to this report.