A total of 170 cannabis factories have been discovered by police in Northamptonshire in the past year.
Between March 1, 2011, and February 29, 2012, officers uncovered 170 cannabis cultivations in the county.
Of these 94 of were in north Northamptonshire.
One of the most recent discoveries was a cannabis factory in a rented home in Apethorpe, near Oundle.
More than 300 cannabis plants were found during a raid at the house on Monday, March 16.
On February 20 police found cannabis plants with a street value of up to £30,000 when they raided a house in Berryfield Road, Cottingham, and in the first six weeks of 2012 police in Wellingborough discovered cannabis being grown at four houses in the town.
Police are urging people – particularly landlords – to be alert, to keep an eye out for the signs of cannabis being grown and to report any suspicions they have of possible cannabis factories to police.
Tell-tale signs include houses with constantly covered windows and condensation on the windows.
A smell of cannabis in the area and tampered electrical wiring are also signs of drug cultivation.
Neighbours are also being encouraged to report their suspicions if they see new occupants of a property carrying large amounts of light fittings, fans and ducting together with large amounts of plant pots and bags of compost.
Sgt Craig Johnson, from Northamptonshire Police’s Operation Guardian crackdown on acquisitive crime, said: “There are often clear tell-tale signs of a cannabis factory, and we would advise people to be aware of these and report any suspicions.
“Often the cost for a landlord to pay for damages to a property once it has been used as a cannabis factory can be in the thousands, which is why we recommend that landlords be alert to new occupants.”