Two Austrian art students were taken into custody and later released after at least three people were injured while trying to kick soccer balls filled with concrete set up by the two in Berlin as part of an art project.

The two, aged 26 and 29, had posted a sign saying"Can you kick it?" near the 15-kilogram (33-pound) balls, all 16 of which were also attached to utility poles, trees or street lights. The duo could now face charges of causing dangerous bodily harm and dangerous interference with traffic.

A lawyer for the men, who call themselves the "LM/LN Media Group," denied the charges saying the balls were clearly marked as pieces of art. The duo argue the signs could be interpreted to have a variety of meanings from "Soccer is something for everyone to soccer is everywhere."

The objects were "neither a source of danger nor a trap" and part of a project called "Concrete Soccer," according to a statement from the two men. The balls were meant to symbolize the mass phenomenon of concrete.

Police confiscated nine of the balls and have no information who removed the other seven.