Initially, it was suggested Neo-Nazi groups could be behind the crime. However Reuters, citing Polish police, writes that financial motives were behind the men’s action.

"We can say that none of the five are members of a neo-Nazi group,” Andrzej Rokita, district police chief in the city of Krakow is quoted as saying at a media conference. “Their intent was undoubtedly robbery-related. We will be able to decide later whether the crime was ordered or whether they acted on their own initiative."

Interfax, citing a Polish FM radio station said the theft was reported early on Friday by the museum’s security guards.

“All this is very sad. The perpetrators either did not know where they were or, what is even sadder, they knew it but that did not stop them from stealing it," a museum employee is quoted as saying.

The five suspects were captured after Polish police launched an intensive search operation, which included border checks and road blocks across southern Poland. About 40 forensics experts were involved in gathering evidence at the scene of the crime. The country also asked international policing bodies – Interpol and Europol – to help recover the sign and find the thieves.

The Auschwitz Museum and Polish authorities offered a reward of about 30,000 euro for the information that could help find the suspects.

The incident was strongly condemned by the international community.

"A worldwide symbol of the cynicism of Hitler's executioners and the martyrdom of their victims has been stolen,” Polish President Lech Kaczynski said. “This act deserves the strongest possible condemnation."

Israeli Prime Minister Benjamin Netanyahu called on the Polish government “to track down these twisted criminals who desecrated a place where more than a million Jews were murdered. It is important to preserve the memory of the crime, and therefore it is important to preserve the crime scene of one of the worst atrocities in the history of the Jewish People and of all humanity," he said.

After the infamous sign went missing, it was replaced by a replica made in 2006, when the original slogan was under restoration. The original iron sign was made by prisoners and put up over the gates in 1940. Daily, crowds of prisoners were made to go to work through the gates with “Work sets you free” slogan, accompanied by music from an orchestra.

Auschwitz-Birkenau – the biggest concentration camp – was built in 1940 in Nazi- occupied Poland to detain and kill prisoners and Jewish deportees from Poland, the USSR, Austria, Belgium, Denmark, France, Greece, Czechoslovakia, the Netherlands, Yugoslavia, Norway, Romania, Italy and Hungary.

The camp was responsible for up to 1.5 million deaths.