WASHINGTON (AP) — The Justice Department says there’s an ongoing grand jury investigation related to a Russian social media troll farm accused of interfering in the 2016 presidential election.

That’s according to a court filing Thursday from prosecutors with special counsel Robert Mueller’s office and the U.S. Attorney’s Office in Washington.

The lawyers told a judge they want to reply under seal to an ongoing court dispute with a Russian company because their response concerns a “matter occurring before the grand jury.”

Mueller’s office last February indicted three Russian individuals and three Russian companies accused in a social media effort to sway American public opinion ahead of the election.