An indictment in special counsel Robert Mueller's investigation into Russian interference in the 2016 election will reportedly be handed down on Monday.

NBC News reported the development on Saturday, citing a U.S. official familiar with the matter.

A spokesman for the special counsel's office declined to comment to The Hill.

It is not known who will receive the indictment or what the charges are.

CNN first reported Friday night that a federal grand jury had approved the first charges in Mueller's probe. The network reported that the charges are sealed under a federal judge's order.

The reports of charges being filed mark a significant milestone in Mueller's investigation into alleged ties between Trump campaign associates and Russian officials.

Mueller was appointed by Deputy Attorney General Rod Rosenstein in May to oversee the investigation.

Earlier this week, White House press secretary Sarah Huckabee Sanders said the White House believes Mueller's probe is "getting closer to conclusion."

"I have not spoken with anybody at the Department of Justice on that front, but I think that we are seeing that it is getting closer to conclusion," Sanders told Fox News's Bill Hemmer.