A federal grand jury has approved the first charges as a result of special counsel Robert Mueller’s investigation into possible collusion between Russia and Donald Trump’s presidential campaign, CNN reported Friday night.

Authorities were preparing to take anyone charged into custody on Monday, CNN reported, citing sources briefed on the matter.

It’s unclear what charges have been filed or who they name. The charges remained sealed Friday under a federal judge’s order.

Mueller, a former FBI director, was given sweeping power in May to investigate Russian interference in the 2016 presidential campaign. His broad mandate could encompass any questionable actions of Trump’s associates and possibly even the circumstances of the firing earlier this year of FBI Director James Comey.

The Justice Department’s appointment of Mueller as a special counsel came amid growing public demands to place the politically charged inquiry into the hands of an outside investigator with bipartisan respect. It also came after weeks of questions about the Justice Department’s independence from the White House. Attorney General Jeff Sessions had to recuse himself because of his own undisclosed Russian contacts during the campaign.

At the time of Mueller’s appointment, the White House issued a statement in which Trump said: “As I have stated many times, a thorough investigation will confirm what we already know — there was no collusion between my campaign and any foreign entity. I look forward to this matter concluding quickly.”

The special counsel’s office declined to comment on Friday, CNN reported.