CANNABIS producers are being targeted by police in an attempt to drive out production of Stoke-on-Trent.

In the past four weeks, officers from Staffordshire Police's serious and organised crime unit have destroyed 15 factories across the city.

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A total of 3,660 plants have been recovered from eight houses, six commercial premises and one farm.

The raids come on the back of Operation Nemesis, a year-long campaign against illegal drugs, which has won national recognition for being the best example of action against street-level dealing.

Now the skills and lessons learned from that battle are being used to fight cannabis farms.

Detective Inspector Jim Wood, from the Stoke-on-Trent division, said: "There has been increased activity in recent weeks targeting the cultivation and production of cannabis. It is a force-wide operation with a new direction.

"In the past we have been a bit reactionary and have mostly caught the people who tend to the plants, known as the gardeners.

"But this time we are looking for the organisers. We are being more proactive in our approach, coming at it from a number of different angles, including stripping these people of their assets and the profits they have made from their criminal activity.

"Invariably the people tending the plants are not the ones reaping the financial reward."

Police have a list of tell-tale signs which indicate whether a property is being used for growing cannabis. They are asking the public to look out for:

Windows permanently covered from the inside

Visits to the premises at unusual times of day or night

People maintaining the house rather than living there

Daily or weekly calls at the property by people who stay for a short time

Black bin bags or laundry bags being taken away

Compost bags or gardening equipment left outside, usually at the rear of the premises

Vents protruding through the roof or a rear window

Strange, pungent smells from the premises

Unusual noises from equipment such as cooling fans.

DI Wood said: "Landlords also have a responsibility. Often they will put a tenant in without doing rigorous checks. It's no good getting someone in and just walking away.

"Many landlords need to be more vigilant. They should contact police at the first indication of a problem.

"Public awareness of police action against cannabis is growing.

"In Stoke-on-Trent a lot of pubs are closing and being boarded up.

"These empty properties create opportunities for cannabis farmers because they have larger rooms, cellars and are still owned by someone else. When a pub has been steel-doored by a brewery, the gangs gain entry, by-pass the electrical supply and grow hundreds of plants.

"Members of the public and people in the business community are our most valuable weapon in this operation.

"A lot of members of the public are familiar with the smell of cannabis, and people are becoming more confident in the police action.

"Cultivation is linked to other criminal activity. These gangs are not concerned with growing small amounts; they are interested in making large sums which they can reinvest in other forms of criminality."

Police have arrested 13 people in connection with the cannabis raids. Eight have been released on bail pending further inquiries and five have been charged with being involved in the production of cannabis.