The first round of charges in special counsel Robert Mueller’s ongoing investigation into Russian meddling in the 2016 U.S. election were approved Friday, according to news reports.

CNN first reported the story Friday night. According to that report,  a federal grand jury in Washington, D.C., approved the charges. CNN cited sources briefed in the matter.

The network said plans were being made to take anyone charged into custody on Monday.

NBC News confirmed the story on Saturday, posting a report that said “Mueller’s Office of the Special Counsel will serve an indictment on Monday though the charges and target are unknown, a U.S. official with firsthand knowledge of the process confirmed to NBC News. The timing was confirmed by a second source familiar with the matter.”

CNN said a spokesman for Mueller’s office declined to comment.

The special counsel has been digging into allegations of Russian involvement in the 2016 presidential campaign since May.

Mueller was appointed to head the investigation by Deputy Attorney General Rod Rosenstein days after President Trump fired then-FBI director James Comey.

Former Trump campaign manager Paul Manafort and former Trump national security adviser Michael Flynn have been reported to be key aspects of the investigation.

President Trump has also been reported to be part of the investigation for possible obstruction of justice for his alleged efforts to impede the investigation.

CNN reported that investigators are also scrutinizing Trump and his associates’ financial ties to Russia.

In addition to Mueller’s probe, three committees on Capitol Hill are conducting their own investigations.