The iron sign bearing the Nazi slogan "Arbeit Macht Frei," the German words for "Work Sets You Free," vanished from the former Auschwitz death camp Thursday night between 3:30 a.m. and 5 a.m. Avner Shalev, the head of the Yad Vashem Holocaust memorial institute in Jerusalem blames neo-Nazis. “We don’t know the identity of the perpetrators but I assume they are neo-Nazis,” he said. He also said the act "constitutes a true declaration of war." Recovery of the sign is seen as "a matter of national honor," and Polish Prime Minister Donald Tusk said hunting down the thieves is "an absolute priority." The sign, which marked the main entrance to the former Nazi death camp in Poland where more than 1 million people died during World War II, had been unscrewed on one side and pulled off on the other.