After occupying Poland in 1939, the Nazis established the Auschwitz I camp, which initially housed German political prisoners and Polish prisoners. The sign was made in 1940 and placed above the main gate there.
Two years later, hundreds of thousands of Jews began arriving by cattle trains to the wooden barracks of nearby Birkenau, also called Auschwitz II, where they were systematically killed in gas chambers.
The sign disappeared under cover of darkness in the bitter cold early Friday.
Less than three days later, on Sunday, police arrested five Polish men they described as common criminals who were likely seeking profit from the sign found in a snow-covered forest 200 miles from where it was stolen.