Hundreds of drug dens - from industrial-scale factories to smaller operations in criminals' own homes - are uncovered in East Anglia each year, an investigation has found.

Hundreds of drug dens - from industrial-scale factories to smaller operations in criminals' own homes - are uncovered in East Anglia each year, an investigation has found.

More than 550 drug-growing operations have been raided by police in Norfolk, Suffolk and Cambridgeshire over the last three years.

In Norfolk alone 109 properties in which evidence of drug production, mostly cannabis, was found were raided in the last 12 months - the equivalent of more than two a week.

The force has also closed down a number of crack dens, which often act as the hub of wider criminal activity in communities.

The figures, released under the Freedom of Information Act, expose the scale of drug production in the region - but police insist that while more operations are operating below the radar they are determined to disrupt drug production as it is often linked to serious crime.

In recent cases judges have warned organised gangs are increasingly looking to rural counties, believing their activities are more likely to go undetected than in large urban centres.

Det Chief Insp Tracey Prowting, of Norfolk police's Drugs and Serious Crime Unit, said: “The work carried out by Norfolk Constabulary to target organised drug dealing and acquisitive crime within our communities has proved successful.

“We are well aware of the effect the misuse of drugs and associated crime can have on a community and have invested a significant amount of time and resources into disrupting this activity.

“A major part of our success has been intelligence provided by members of the public. We reiterate the message - the more people tell us, the more we can do to tackle drugs and track down the people involved.

“Our actions have seriously inconvenienced the drug dealing networks but there is still more to be done and those who persist can be assured they will be tracked down and stopped.”

The majority were found in neighbourhoods around Norwich, Great Yarmouth and King's Lynn but other hotspots included Fakenham and Swaffham, as well as a number of more rural locations.

In many cases London-based gangs and groups with Asian origins have targeted rural areas.

Most cases involved the production of cannabis but at several properties evidence of the production of other class B drugs, such as amphetamines was found.

Discoveries last year included a factory with a potential annual yield of �415,000 in Pottergate Lane, Aslacton, near Long Stratton. Police found 560 cannabis plants at a house taken over by illegal Vietnamese immigrants.

In March a farm with more than 300 plants was discovered in Wilks Farm Drive, Sprowston, near Norwich. A Vietnamese man was arrested and charged. A similar Vietnamese-run operation with an annual yield of �120,000 was found in Beccles Road, Gorleston, in December 2008.

The figures include everything from home owners who grow their own supplies of cannabis to operations run by organised gangs.

Research by Norfolk's drug unit reveals 23 of the larger drug “factories” have been discovered since March last year. The force has also closed down seven crack dens since 2003.

Over the same period Cambridgeshire police have uncovered cannabis production at 100 properties, including several in the Wisbech area, but the figures do not reveal the size of the farms.

In Suffolk, police uncovered 18 farms where 15 or more cannabis plants were found, including two in Lowestoft.

The National Landlord's Association (NLA) has warned gangsters are increasingly targeting rented properties to grow cannabis and manufacture crystal meth. There have also been a number of cases in which farm out-houses or old industrial premises have been used.

David Plaister, NLA member, said: “If they are caught it is not the criminal tenant who has to foot the bill for damages to the property but the landlord.”

The NLA recommends that landlords carry out thorough check adding that, if they suspect their tenants of criminal activity, they should not confront them but go straight to the police.