During surveillance this weekend, officers say they smelled a strong odor of cannabis at a building on Aambeeldstraat in Edam.
They investigated the business building, a car parked in front of the building and the people who were there. For example, equipment was discovered with which hemp is grown.
Six men aged between 39 and 46 have been arrested and their roles are being investigated, police said.
The grow room has been safely cleared and the equipment is being destroyed. The six have been released, but remain suspects.