POLICE smashed a major cannabis-growing operation in Southampton – almost by accident.

Officers investigating a suspected burglary discovered the first “factory”. Then while carrying out door-to-door inquiries at neighbouring homes they stumbled on a second.

About 600 plants with a potential street value of around £120,000 were seized from the two properties – which had both been specifically converted.

The drama began shortly before midnight on Friday when several officers went to a semi-detached property near the railway bridge in Bitterne Road West, Southampton, after reports of a disturbance inside.

Entering through the back door, they not only found five intruders – four men and a woman – at the scene but were also astonished to find the house had been adapted into a cannabis production factory.

Nearly 300 plants were crammed into three bedrooms, the lounge and dining area.

On Saturday morning, they made their second huge find as they conducted house-to-house inquiries in nearby Rampart Road.

They knocked on the front door of a detached house and got no answer, but on lifting the letterbox to see inside, they recognised the distinctive smell of cannabis.

Again, they found two men inside as well as about 300 plants growing in the three bedrooms and two downstairs rooms.

Several police vehicles were parked in Rampart Road during the day as scenes of crime officers carried out their investigations.

During the afternoon, traffic along the busy main road had to be halted for a lorry to be reversed into the drive to pick up a skip.

Det Sgt Paul Gelman said it bore the hallmarks of a professional operation.

The discovery comes amid fears that gangs are again targeting Southampton as a major drug producing centre.

So far this year, 13 properties – each three or four-bedroom privately rented houses in Portswood, Shirley and the city centre – have been uncovered.

Hundreds of plants have been seized before the gangs could chop them up and sell them.

In 2007 more than 50 cannabis factories were found in the city and the crown court heard that Vietnamese men were being recruited in London shortly after arriving in England and transported to the Southampton area where they acted as “gardeners”

in exchange for food and lodgings.

As reported in the Daily Echo, police last week launched Operation Closed in a bid to wipe out the menace and alert landlords about how properties are being rented out for criminal purposes.

Seven people remain in custody helping police with their inquiries after the two most recent finds.