The iron sign with the text 'Arbeit macht frei' has been returned to the site of the Nazi's Auschwitz extermination camp in Poland.

The sign was stolen last month and sawn in three. It was recovered a couple of days later and five people were arrested. Polish police say the thieves planned to demand a ransom for the pieces.

The Auschwitz museum is looking into when the sign can be secured in its place above the entrance to the former Nazi concentration camp.

photo: Auschwitz entrance (EPA)