A U.S. grand jury returned an indictment against a Russian woman on Tuesday, and added a charge accusing her of acting as a Russian government agent while developing ties with American citizens and infiltrating political groups.

Maria Butina, who studied at American University in Washington and is a founder of the pro-gun Russian advocacy group Right to Bear Arms, was charged in a criminal complaint on Monday with conspiracy to take actions on behalf of the Russian government.

Tuesday's grand jury indictment added a more serious charge of acting as an agent of the Russian government, which carries a maximum penalty of 10 years in prison. The conspiracy charge carries a maximum five-year prison term.