A federal grand jury in Washington has approved the first criminal charges in the special counsel’s investigation into Russian election interference, two sources told NBC News, marking a significant milestone in an inquiry that has roiled Donald Trump’s presidency.

Mueller’s Office of the Special Counsel will make public an indictment on Monday, a U.S. official with firsthand knowledge of the process confirmed to NBC News, without disclosing the name of the target or the nature of the charges. The timing was confirmed by a second source familiar with the matter.