Late Friday evening, CNN reported that a federal grand jury had approved charges in the investigation by special investigator Robert Mueller into connections between the Trump campaign and the Russian government. It is unclear who is being charged, or what the charges are at this point.

CNN reports:

The charges are still sealed under orders from a federal judge. Plans were prepared Friday for anyone charged to be taken into custody as soon as Monday, the sources said. It is unclear what the charges are.

A spokesman for the special counsel's office declined to comment.

Mueller was appointed special investigator after Attorney General Jeff Sessions recused himself from any investigation into Russian election interference based on his testimony regarding Russia; deputy attorney general Rod Rosenstein then recused himself and appointed Mueller after President Trump had him write a memo serving as the basis for the firing of then-FBI Director James Comey. Trump later told members of the Russian government that Comey’s firing had relieved pressure on him.

CNN’s report is skeletal, but it does include the following details:

On Friday, top lawyers who are helping to lead the Mueller probe, including veteran prosecutor Andrew Weissmann, were seen entering the court room at the DC federal court where the grand jury meets to hear testimony in the Russia investigation. Reporters present saw a flurry of activity at the grand jury room, but officials made no announcements.

Speculation at this point has focused on former Trump national security advisor Mike Flynn, and former Trump campaign manager Paul Manafort. Manafort was apparently threatened with indictment earlier this year.

Mueller has been under heavy fire from Republicans, with serious calls for him to step down from his position amid allegations that the FBI used the so-called Steele dossier, compiled by Fusion GPS at the behest of the Clinton campaign, to target Trump campaign officials.