A reward of €500,000 is being offered for information about this summer’s jewel theft at the Tefaf fine art fair in Maastricht, the Telegraaf has reported.

The money has been put up by the insurance company and will be paid if the items, thought to include a rare large yellow diamond, are recovered, the paper said.

The police are continuing to hunt for four men, who wore flat caps and glasses as they smashed open the display case during the fair in June. Another brandished a gun at visitors.

Police have confirmed that the gang made off with a quantity of jewelry but have not said what. According to the Telegraaf, the haul included at least 10 items, including a necklace with the 114 carat diamond

The reward, which according to broadcaster NOS has been confirmed by the police, is one of the highest ever offered in the Netherlands.

The public prosecution department earlier offered €100,000 for information leading to the address of crime boss Ridouan Taghi while a private foundation put up €1 million to try to solve the cold case murder of Tanja Groen.

The public prosecution department only pays out roughly 10% of the reward money it has offered, the NOS said.