The discovery was made by the landlady of a rented house, on Hall Street in the Llangollen, who visited the property after reading, in the Evening Leader, about a similar 'factory', at a supposedly empty house near the village of Trevor, which was found earlier this week.

When the landlady went to the property on Hall Street she found a padlock on the door and saw growing apparatus through the window.

She contacted police and officers found it had been taken over by a hydroponics system and closed the scene down immediately. A forensic team were carrying out an investigating at the house today (July 24).

Sergeant Mavis Evans said: "The landlady attended at the property and discovered a suspicious lock on the door and when she looked through the windows she could see the lighting equipment.

"She contacted us and we have found at least two large rooms containing a number of plants which are larger than those discovered on Tuesday."

Two people have been arrested in connection with the discovery in Hall Street

Earlier this week the owner of Plas-yn-Pentre, an ancient house near Llangollen, discovered that the supposedly empty building had been broken into and that a cannabis factory had been set up over its three floors.

The culprits had boarded up the house's windows and it is thought that more than 600 plants were found by police.

They had also caused damage which, due to the nature of the historic building, the owner has estimated could cost more than £10,000 to put right.

Two people, a man and a woman, both described as being of oriental appearance, were said to have been seen acting suspiciously at the property.

Police are now asking landlords and owners of empty properties to ensure their premises are not being used illegally.

Sgt Craig Jones said: "It is well known that organised crime gangs, particularly those involved in drug production seek to distance themselves from any illegal activity to avoid being arrested. A convenient way of doing this is involvement in rental premises."

"Our aim is to ensure that landlords are not being abused and that their premises are not being used for illegal drugs."

Sgt Jones added: "Any landlord who may suspect there is drug activity going on in a rented property is urged to contact the police immediately. We would advise them not to confront the tenants and not to disturb the factory."

Anyone with any information about the cannabis factories at Hall Street or Plas-yn-Pentre is asked to contact North Wales Police on 0845 6071001 (Welsh language line) or 0845 6071002 (English language line) or Crimestoppers anonymously on 0800 555 111.