The heist took place early Sunday morning. A gang of masked thieves broke into the museum's jewellery room and smashed six display cases, according to a source familiar with the investigation.
About 20 pieces of jewellery were stolen. The value of the loss is being determined but could amount to several million euros, probably closer to four million, the source said.
Four million euros corresponds to 44 million Swedish kronor.
This comes just a few months after a high-profile jewel heist at the Louvre in Paris.
According to sources, the stolen items were crystal jewellery, which means they cannot be melted down.
No one has been arrested yet.
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