“We do not have any information, we are not in touch with Polish authorities,” detective-inspector Christian Pena of the Swedish criminal police told AFP.

Meanwhile, Swedish tabloid Aftonbladet reported on Thursday that the sign was to have been transported to Sweden for sale, the proceeds of which would have been used to finance a nazi attack against Swedish political leaders prior to the 2010 elections.

Säpo, the Swedish intelligence service, confirmed the existence of a militant Nazi group, saying that “measures had been taken” against the threat.

Polish investigators said Tuesday that a foreign resident was the mastermind behind the theft, but refused to confirm Polish news channel TVN24’s report that the trail led to Sweden.

Pena said Swedish police only had the information they had seen in the media coverage of the theft. Polish police recovered the metal sign – which means “Work Will Set You Free” in German – on Sunday in northern Poland, three days after it disappeared.

Polish police said they arrested five men who may have been working for a neo-Nazi collector.

According to Pena, Swedish police who would have been aware of any cross-border investigation have not been involved.

Poland contacted Interpol and its European equivalent Europol after the theft at the former World War II concentration camp where about 1.1 million mainly Jewish detainees were killed.