Poland will formally seek Sweden's help in investigating the theft of the "Arbeit Macht Frei" sign from the Auschwitz memorial, confirming that Polish authorities suspect a Swedish link in the crime.

Boguslawa Marcinkowska, a spokeswoman for Krakow prosecutors, says her office will send a formal request for help Wednesday to the Swedish Justice Ministry in Stockholm.

Polish media have been reporting that the theft was commissioned by a collector living in Sweden, but investigators have not confirmed that.

The sign, which means "Work Sets You Free," was stolen earlier this month and found two days later cut into three pieces. Police have arrested five men whom they described as common criminals who likely stole the sign on a commission from abroad.