A grand jury approved the first charges in the federal investigation into Russian meddling in the 2016 presidential election, according to multiple reports.

It's unclear who has been charged, and with what. CNN reported Friday that the charges are sealed under orders from a federal judge. Some of those charged may be taken into custody as early as Monday.

More:Special counsel Robert Mueller's grand jury raises stakes in Russia investigation

Related:Robert Mueller using multiple grand juries in Russia inquiry

Special counsel Robert Mueller has tapped at least two grand juries — in Virginia and Washington, D.C. — to advance a wide-ranging federal inquiry into possible coordination between President Trump's campaign and Moscow during the election.

CNN said its reporting is based on sources who declined to be identified. Reuters and The Wall Street Journal also confirmed the reports with sources speaking under anonymity.

Peter Carr, a spokesman for the special counsel's office, declined to comment on Friday.

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

Trump has repeatedly denied any collusion with Russia during the campaign and has called the investigation a witch hunt.

Shortly after Trump abruptly fired then-FBI Director James Comey in May, the Justice Department appointed Mueller as special counsel. Mueller took the reins of a federal investigation that Comey first opened in July 2016 in the middle of the presidential campaign.

Contributing: Kevin Johnson