West London has seen an increase in the number of cannabis factories, say police.

The Met says cannabis factories exploit those operating them and are associated with gang activity that can lead to crime and anti-social behaviour.

In a bid to crack down on the proliferation of cannabis farms, the Met's West Area BCU – which covers Hounslow, Ealing and Hillingdon boroughs - has issued guidance on what to look out for if you suspect a cannabis farm in your area.

Bright light – The cultivation of cannabis plants requires a lot of light running at around 12 hours per day. The lights are incredibly bright so a tell-tale sign is any property where windows are constantly blacked out or curtains are never opened.

Fans/Ventilation – The farmers need to ventilate the plants they are cultivating and they do this using large extractor fans which make a low humming sound. Routine use of a fan such as this, particularly in autumn or winter, would be an indicator that a cannabis grower may be operating at the property.

Smell – While it takes three months to grow a crop of cannabis, it is during the final month that the smell becomes overpowering – it is pungent and quite literally stinks.

Comings and goings – Many cannabis farms don't have anyone living at the address; be aware of people coming and going at strange times and not staying for long.

Sergeant Keith Flowers of the West Area Command Neighbourhood Tasking Team said: "Cannabis production is a generator for organised crime and exploits those who grow it. It is associated with gang activity and increases anti-social behaviour in our neighbourhoods.

"We have often found that electricity supplies are tampered with, additional security is installed which may include additional locks, grilles and CCTV cameras. Often the windows are covered over and you may notice people coming and going from the property at unusual times.

"If you believe that there is a cannabis factory operating near to your home we ask that you report your concerns by dialling 101. Alternatively you can call Crimestoppers anonymously on 0800 555 111.''

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