TO the unsuspecting eye they look just like any other Southampton houses.

But take a closer look and there is something slightly unusual about the handful of older-style properties that permanently have their curtains drawn and condensation seeping down the windows.

It is houses like these, owned and put on the rental market by unknowing landlords, that have become the target for organised crime gangs who set about transforming them into cannabis farms.

This morning a team of officers from Southampton's drug investigation team busted yet another makeshift factory in the city - the 48th in the last 18 months. Inside the property in Arnold Road, Portswood virtually all of the rooms had been converted to grow the drug.

The Daily Echo joined detectives as they forced their way into the property through the rear patio doors shortly after 8am, carrying out a brief check to make sure the premises were safe and to see if anybody was inside.

One of the two rooms downstairs was clearly being used as living quarters with food and a lighted candle inside.

Upstairs two bedrooms had been completely stripped out.

One contained scores of new plants that were growing under dozens of lights while the other was being used to dry out the drug which lay in piles all over the floor. Even the bathroom was packed with implements used to harvest the cannabis.

Det Sgt Will Whale said: "We have found what is described as a cannabis farm - a place that has been used for the growth of cannabis.

"This is a wholesale problem in the city and today we haved uncovered a large quantity of young plants and there is clear evidence that these premises were being used to harvest cannabis in an industrial set up.

"The electricity has been tampered with and the place is a major fire risk."

Following the raid electricity board officials were called to turn off the power supply to the property.

It was back in November 2005 when detectives stumbled upon the first factory of its kind in the city.

The sheer number of identical premises uncovered since then has astounded officers and left the city dubbed the cannabis-growing capital of the south.

Today a total of 48 such farms have been busted in the city - more recently at a rate of up to two a week.

A total of 14,755 cannabis plants have been seized, which could have had a street value of almost £2.4m if they had been fully grown and the resulting crop sold on the street.

That is the largest amount of herbal cannabis recovered in Southampton in almost a decade - and it is thought that those responsible are targeting the city because it has two universities and therefore an affluent property rental market.

Although it does exist in other parts of the county, the problem does not appear to be anywhere near as big as in Southampton.

It is a major money-spinner for the individuals behind the farms.

Although they are spending an estimated £20,000 transforming the properties, they could easily expect to reap up to 20 times that amount - in the region of £400,000 - should they manage to successfully grow all of the hundreds of plants and get the drug out on to the streets without being caught.

However, it is a financial nightmare for the unsuspecting landlords who are being duped into renting out their multiple-bedroom homes to people they believe to be genuine tenants - and are left picking up bills that run into thousands of pounds.

Det Insp Dave Morgan, based at Southampton's Priority Crime Unit at Hulse Road, said that organised crime gangs behind the farms appear to be operating in virtually the same way each time.

The "tenants", who are sometimes foreign nationals who speak good English, will normally arrange to meet a landlord in a public place, like a local pub, where they will furnish them with references and offer the cash for rental or set up a direct debit for monthly payment.

Once they have moved into the property they will appear to live normally for a couple of weeks or months before the major work to convert the rooms into a factory is carried out, severely damaging the interior of the homes along the way.

Locks are changed, plastic sheeting laid over the flooring, and the walls lined with foil.

The floorboards are uprooted to get to the electricity supply, where clamps are dangerously put over the cables to bypass the meter supply - causing a major fire hazard which in recent months has seen properties completely burnt out.

Inside each room there are scores of plants, all at different stages of growth - and the majority if not all destined for the streets of the UK.

"It's a very professional outfit that is ultimately run like a lucrative business. Cannabis factories like these are very much organised crime which feature on a national level," said Det Insp Morgan.

"When you have a lot of available for-rent accommodation then the city or town can become vulnerable to this type of crime.

"We have found links with several other places in the UK since we began uncovering these factories in Southampton. We never expected to be dealing with anything on this sort of scale 18 months later."

A number have already been jailed for their part in creating and running the factories busted in South-ampton, while others are still going through the courts. In the background there are other people paying a heavy price for this crime.

Det Insp Morgan said: "The people who are really losing out in this are the landlords of these properties who are finding themselves landed with massive bills to repair the significant damage caused to the property, and costs incurred by the Electricity Board to make the premises safe from the National Grid.

"Landlords have been left with bills to pay, on occasions between £20,000 and £40,000. We need to get the message out there that they are accountable, and must be vigilant on who they are letting their houses to."

When the first converted house was discovered in Claremont Road, Shirley, in November 2005, the alarm was raised by a couple with young children who reported a strong, sickly smell coming from a neighbouring property.

Intelligence not only comes from neighbours but from suspicious landlords who can't access their properties, as well as electric companies whose suspicions are raised.

Det Insp Morgan said: "Of late we have been uncovering between one and two cannabis farms a week in the city. In total we have seized 14,755 plants and 242 kilos of dried cannabis, with a total street value of £2,399,950,000.

"It should be a concern for landlords who are, in the end, responsible for their own properties. Quite often they are looking for a short-term gain and are tempted when a genuine-looking person offers them cash for the rent. They can be taking between £600 and £1,000 a month - but the price they can end up paying is so much more."