Hundreds of thousands of people passed under the sign to their deaths
Polish police want to question two Swedes over the theft of the "Arbeit macht frei" metal sign from the Nazis' notorious Auschwitz death camp.
Polish prosecutors say one is believed to be the mastermind behind the theft, while the other helped with logistics in the 18 December operation.
The sign was later found by police cut into three pieces, and five Polish men were arrested in the country's north.
Polish authorities have said the theft was ordered by a foreigner.
"We have asked Sweden to confirm the personal data of two people we suspect of participating in this crime and we want to question a third person from Sweden as well, but this person has no direct link with the case," Prosecutor Artur Wrona told a Krakow press conference on Wednesday.
'Incitement to theft'
There has been speculation in Swedish and British media that the theft was ordered by neo-Nazi sympathisers, but there was no confirmation of this from Mr Wrona.
He said the next steps would depend on the Swedes, from whom Polish authorities earlier requested assistance in the case.
None of those arrested are thought to be part of a neo-Nazi group
"One (of the two sought) is the mastermind behind this theft and the other is the one who brought the car to Poland which later served during the robbery."
"We believe we have enough evidence to be able to press a charge of incitement to theft against at least one of these people and perhaps against both."
The sign, which weighs 40kg (90lb), was half-unscrewed, half-torn off from above the death camp's gate.
The 5m (16ft) wrought iron sign - the words on which translate as "Work sets you free" - symbolises for many the atrocities of Nazi Germany.
The theft caused outrage in Israel, Poland and around the world. More than a million people - 90% of them Jews - were murdered by the Nazis at Auschwitz in occupied Poland during World War II.