 The second genocidal activity, between December 1941 and May 1942, involved the incarceration of the women and children at the Semlin concentration camp and former fairgrounds in Belgrade and their gassing in a mobile gas van called a Sauerwagen.The German concentration camp, the old fairgrounds or Stare Sajmište, near Zemun was established across the Sava river from Belgrade, on the territory of the Independent State of Croatia, to process and eliminate the captured Jews, Serbs, Roma, and others.Some 7,000 to 10,000 Jews are estimated to have been exterminated by the Nazis in the Semlin concentration camp alone, along with more than 10,600 Serbs and uncounted Romani (see Sajmište concentration camp).