Cannabis smelling “scratch and sniff” cards are being distributed by police officers in Northern Ireland to help shut down the increasing number of factories making the drug across the region.

The PSNI said the cards would help the public detect cannabis production plants.

The scratchcard contains an element that replicates the smell of cannabis in its growing state, which is a different smell to when it is being smoked.

Police are distributing the cards after crime figures revealed a 44% increase in cannabis factories across Northern Ireland in 2013-14.

The PSNI discovered a total of 130 cannabis factories last year, and so far this year 49 factories have been found. It has also produced a video available online that advises the public on how to recognise the signs of cannabis factories in an area.

The signs on the “scratch and sniff” cards for cannabis factories include:

• A strong sickly sweet smell.

• Covered or blacked out windows around a property.

• Constant lighting day and night.

• High levels of heat and condensation.

• Constant buzz of ventilation.

• Excessive amount of cables.

Beside the circle on the card where the public can “scratch and sniff” the cannabis odour is an assurance from the PSNI that “it’s completely safe; there are no drugs in the card, it’s just the smell of the plant”.