Municipal authorities in the Netherlands think citizens can help uncover illegal cannabis growers in Rotterdam and The Hague.
They are distributing marijuana-scented scratch cards to about 30,000 households in the cities so that people can recognise smell of cannabis. This would help them report those growing marijuana.
The authorities suspect more than 40,000 people across the country grow the plant secretly in basements and attics.
When scratched, the card gives off the scent of marijuana and a police number. It also informs that growers use cables and lamps to maintain a cultivation temperature of 27°C inside the house, which could lead to fire accidents.
The card advises people to keep an eye for indicators like buzzing sound of ventilators and suspicious connections to electricity supply point. The Dutch government decriminalised possession of up to five gramme of cannabis in 1976, but bulk cultivation and retail remain illegal.