Acting Assistant Chief Constable George Wilson, of Thames Valley Police, said: "During the last 12 months, Thames Valley Police has seen a marked increase in Vietnamese linked cannabis houses.

"In the majority of cases an ordinary terrace or semi-detached house is specifically bought or rented for the sole purpose of growing cannabis.

"The house is then kitted out with special hydroponic equipment, which is then used to produce up to £70,000-worth of cannabis every 11 or 12 weeks."

Police also warned of electrical hazards as a result of cannabis production.

"In many cases the electricity is bypassed which could cause electrocution or even a fire.

"It is in the landlords' interests to keep a close eye on their property and report anything suspicious to the police," he added.

Anyone suspecting there is a cannabis factory in their area is asked to contact police on 0845 8505 505 or Crimestoppers anonymously on 0800 555 111.