A massive cannabis ‘factory’, housing plants estimated to be worth hundreds of thousands of pounds, has been discovered in a row of terraced houses at Clydach near Abergavenny.

The factory occupied three levels in three adjoining properties on Main Road, filling the basement, ground floor and first floor rooms.

A senior police officer described the scale of production as ‘huge’ - the biggest operation of its kind he had seen in a 20-year career.

Gwent police were alerted by a call on November 9 at around 3.20pm from the utility company supplying electricity to the properties.

Further investigation found that the three houses, linked together via their basements, contained approximately 750 cannabis plants at various stages of growth.

One man, aged 18, from Vietnam, has been arrested on suspicion of producing a Class B drug and has been granted police bail, pending further enquiries. Others, including a local man believed to have been living at the property, are assisting the police with their enquiries.

Police are also waiting to interview the landlord.

Inspector Huw Jones told the Chronicle, “Once Western Power had made the premises safe scenes of crime officers went in to carry out forensic tests - taking photos and samples.

“It was quite an established factory - the largest I’ve seen in my entire career.

“The properties were then cleared of the plants and the lighting, heating and fanning devices used to grow them. The whole operation took an entire week.”

He said the smell from the cannabis plants (which will now be destroyed) was really strong, even outside the properties.

“Investigating officers returning from the scene reeked of the stuff. It lingered in the building for days, giving everyone a headache!” he said.

If anyone has any further information, please call Gwent Police on 101, quoting log number 260 9/11/15.