Most of the cases filed against rioters so far were for less serious offenses involving being inside the Capitol illegally, and many defendants were released within a day.
The sweatshirt also bore a skull and crossbones and the words "Work Brings Freedom" - echoing the German slogan atop the main gate at the original Auschwitz camp.
Counterterrorism officials are joining the investigation, as evidence mounts suggesting at least some of the rioters openly plotted to kidnap or harm lawmakers.
In a civil lawsuit in U.S. District Court in Delaware, the government said Walmart failed to take its gatekeeping duties as a pharmacy seriously, allegations the company rejected.