Thieves broke into the premises of the Flemish youth movement Chiro Flanders in Kiewit, near Hasselt, on Saturday, making off with €35,000 in cash and various other items.
The robbery took place on Saturday evening during a party, but it was not until around 1.15 pm on Sunday that signs of the intrusion were discovered.
In addition to the cash, the thieves stole fireworks darts, a safe, a projector, and party equipment.
Local police from the Limburg area have launched an investigation.
