On July 22, 2014, the two American flags on the flagpoles atop each tower were found to have been replaced by bleached-white American flags. Initially, cannabis activism was suspected as a motive, but on August 12, 2014, two Berlin artists claimed responsibility for hoisting the two white flags, having switched out the original flags with their replicas. The artists said that the flags were meant to celebrate "the beauty of public space" and the anniversary of the death of German-born John Roebling, and they denied that it was an "anti-American statement".