Seven paintings by master artists like Pablo Picasso, Claude Monet and Henri Matisse were stolen from a museum in Rotterdam on Tuesday.
According to local police, the alarm system at the Kunsthal Museum went off shortly after 3 a.m., but when the police arrived minutes later, the art works had vanished.
The police are currently investigating how one of the biggest art heists in the Netherlands' history took place.
The museum has been displaying a new exhibition of more than 150 modern art pieces belonging to the private Triton Foundation.
If the seven paintings were sold at auction, they would be expected to fetch hundreds of millions of euros.