The federal grand jury being used by Special Counsel Robert Mueller in the investigation into Russian meddling in the 2016 presidential election has approved the first charges stemming from the investigation, sources tell CBS News.

The indictment is currently under seal but is expected to become public as early as Monday. The nature of the charges is not clear, nor is the identity or number of individuals targeted.

CNN first reported the approved charges Friday night.

Peter Carr, a spokesman in the special counsel's office, declined to comment.

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Deputy Attorney General Rod Rosenstein's office declined to comment on whether he was briefed on possible charges. Rosenstein oversees the Mueller probe at the Justice Department.

There was a flurry of activity Friday at the courthouse where the grand jury is meeting. Andrew Weissmann, a special staff attorney for the special counsel, was spotted at the courthouse. Weissmann spent much of his career at the Justice Department and recently served as the chief of the fraud section of the criminal division.

Rosenstein appointed Mueller in May to lead the investigation into Russian meddling after FBI Director James Comey was fired by President Trump. Comey led the investigation until his firing. Attorney General Jeff Sessions has recused himself from the investigation.

Mueller has wide latitude to examine matters arising from the investigation, and he has also been looking into any collusion by anyone associated with the Trump campaign with Russia. Targets of his investigation include former campaign chairman Paul Manafort and former National Security Adviser Michael Flynn, among others.

CBS News' Andres Triay, Paula Reid, Pat Milton and Clare Hymes contributed to this report.