On 16 November 1943, the Allied air forces dropped more than 400 bombs on the site. The Allied air raid prompted the Nazi government to move all available heavy water to Germany for safekeeping. On 20 February 1944, a Norwegian partisan sank the ferry M/F "Hydro" carrying heavy water across Lake Tinn, at the cost of 14 Norwegian civilian lives, and most of the heavy water was presumably lost. A few of the barrels were only half full, and therefore could float, and may have been salvaged and transported to Germany.