Members of the the far-right group Proud Boys march to the U.S. Capitol Building in Washington, U.S., January 6, 2021.
Members of the the far-right group Proud Boys march to the U.S. Capitol Building in Washington, U.S., January 6, 2021. Reuters / Leah Millis

U.S. federal prosecutors warned on Tuesday there is still a chance they could bring additional criminal charges in their case against the Proud Boys over their roles in storming the U.S. Capitol last year, in a failed bid to block Congress from certifying President Joe Biden's election victory.

"We did indicate the possibility of a third" superseding indictment, prosecutor Luke Jones said during a virtual hearing in the U.S. District Court for the District of Columbia.

"We obviously can't speak for the grand jury or know exactly how things will transpire, but we also don't want to hide the ball."

Tuesday's hearing came a few weeks after a grand jury returned a second superseding indictment charging former Proud Boys chairman Enrique Tarrio for the first time with conspiracy in connection with the Jan. 6, 2021, attack on the Capitol.

Tarrio was added as a defendant along with other Proud Boy members Ethan Nordean, Joseph Biggs, Charles Donohoe, Zachary Rehl and Dominic Pezzola.

They now face charges of conspiring to block Congress from certifying Biden's election win, among other things.

Several of those members were arraigned on the new charges on Tuesday, though Tarrio's lawyer asked for a weeklong postponement.

A new date for Tarrio's arraignment was scheduled for March 30. Last week, a U.S. magistrate judge in Miami ordered that Tarrio should remain detained pending trial.

Federal prosecutors on Tuesday also indicated they would like to postpone the May 18 trial date for the case, in light of recent developments. In their filing, they also cited the possibility of a third superseding indictment, "based in part on evidence seized on March 8, 2022."

The filing said this could lead to charges against new defendants and/or additional charges against the current defendants.

U.S. District Judge Timothy Kelly said he wanted to hold off setting a new trial date for now, and some defense attorneys expressed concern it will be hard to schedule a new date - especially if more people are charged in the case.