A federal grand jury on Friday approved the first charges in the investigation into alleged Russian meddling in the 2016 U.S. presidential election, a source briefed on the matter said.

The indictment was sealed under orders from a federal judge, so it was not clear what the charges were or who the target was, the source said, adding that the indictment could be unsealed as early as Monday.

The filing of charges by the grand jury in Washington was first reported by CNN, which said the target could be taken into custody as soon as Monday.