Chicago police discovered a cache of water bottles containing human waste earlier this month. Sunday they arrested 7 protesters who may have been using them.
Chicago Police arrested about seven people prior to a 2 p.m. march that began at Grant Park.
A spokesperson for Chicago Police Command Center said the arrested protesters were found with bottles filled with urine and feces.
Police declined to comment on the affiliation of those arrested.
For the most part, the largest protest has been peaceful as an estimated 1800-2200 demonstrators march down Michigan avenue.
Chicago Police Superintendent Garry McCarthy said earlier Sunday that he was happy with his department.
"It's a very big job but we are a very big deptartment," he said. "We are well trained and well equipped"
Around 3:15 p.m a group of Black Bloc anarchists broke off from the march and attempted to scuffle with police, but the situation was quickly contained.