From the outside they look like normal family homes, one an imposing townhouse overlooking Yarmouth's St George's Park and the other a small terrace in the resort's Anson Road.

From the outside they look like normal family homes, one an imposing townhouse overlooking Yarmouth's St George's Park and the other a small terrace in the resort's Anson Road.

They have been rented to friendly people posing as a family, and timer switches fixed to televisions and lights provide further reassuring signs of normal domestic activity designed not to arouse the suspicion of neighbours.

It is only when you step through the front door that you notice the pungent smell of mature skunk cannabis plants and discover every inch of living space has been transformed into a professional drugs factory with expert watering systems and heat lamps, powered by illegally tapping into the electricity supply.

Police swoops on the properties by Yarmouth's tactical team over the past two days resulted in one of Norfolk's biggest seizures of cannabis in years with an estimated street value of £200,000.

Two Vietnamese nationals, a 48-year-old man and a 45-year-old woman, were arrested in the first raid in St George's Road this afternoon, and Det Insp Stuart Armes said they were now actively investigating links to a multi-million pound Vietnamese drugs network operating across the country.

Coming in the wake of about dozen other Vietnamese-related cannabis seizures across Norfolk in the past 18 months, the latest seizures point to a disturbing new crime trend in the region.

And as the suspects continued to be questioned at Yarmouth police station yesterday, Det Insp Armes admitted it was possible their investigations could lead to further similar drugs factories in rented houses being found in the town.

In the first raid more than 1,000 mature plants and seedlings were discovered and a similar quantity was discovered in today's swoop.

Each house was set up in a similar fashion with separate growing rooms for seedlings through to mature plants to provide a constant marketable crop.

The timer switches and expert way the electricity meters had been bypassed - described as a “professional job” by police - followed a pattern found in other Vietnamese-related operations. The way the homes had been rented to people posing as a family also fitted the pattern.

Det Insp Armes said the raids followed a host of recent smaller drugs seizures in the area and highlighted the positive impact of the Force's neighbourhood policing strategy - introduced over the past two years - in gathering intelligence from the public.

He said: “Neighbours are best placed to see if something is amiss and we would ask people to look out for black bags at windows or curtains drawn all the time, or homes with very few people coming or going.”

The intense heat of the factories - using huge quantities of electricity - also led to tell-tale condensation on the windows.

Det Insp Armes said Norfolk Police were determined to clamp down on such activity and he warned that anyone running a drugs factory could expect a knock on the door.