Prosecutors are pursuing a wider conspiracy case against the Oath Keepers, charging six more people with links to the far-right militia for their alleged roles in last month’s violent breach of the U.S. Capitol.

A new indictment filed on Friday added to growing evidence that members of extreme right-wing groups planned and coordinated the Jan. 6 assault in Washington, gathering battle supplies beforehand and communicating as they moved through the building.

The charges built on an indictment the U.S. filed against members of the Oath Keepers last month and amounted to the largest conspiracy case over the riot that the U.S. has brought so far, expanding the number of alleged participants from three to nine. Some of the defendants "donned paramilitary gear” and arranged themselves in a martial "stack formation” as they conspired to stop Congress from certifying the election results, prosecutors said.