A £250,000 cannabis factory set up by a Vietnamese drugs gang has been discovered in a disused pub.

Five first floor rooms at the Merrie England, Great Harwood, were kitted out in a high-tech system of lighting and ventilation systems for growing the drug.

Around 1,500 cannabis plants were found when police raided the premises in St Hubert's Road along with more than 20 large black bin bags of cannabis which had already been cultivated.

Police said the expensive electronics that were found in the venue, which closed to customers eight months ago were worth around £50,000.

And they said that the drugs themselves could be worth as much as £200,000.

Police believe the pub, which is currently owned by London developers, had been broken into and was being operated as a drugs farm by Vietnamese gangs. Vietnamese magazines and literature was found on the premises but nobody has been arrested.

Officers believe that the farm has been in operation for at least six months because the amount of equipment and drugs found at the premises.

Sgt Steve Bury said the drugs factory was one of the largest he had seen and it was the first time he had heard of people breaking in to a building in East Lancashire to grow cannabis.

He said: "There is some very high tech equipment being used. It is a very crude set up but an expensive one and there is a huge amount of cannabis."

In the pub there were five rooms dedicated to growing cannabis.

One was full of around 100 small plants, another had almost 1,000 medium sized plants while another room had hundreds of fully mature plants.

In two other rooms it appeared that hundreds of cannabis plants had recently been cultivated.

Each room was kitted out with lamps and ventilation systems with hundreds of plugs and electric wires used to keep the plants growing.

As well as a sophisticated ventilation system all windows were covered with paper so people could not see in.

The cannabis was discovered on Thursday night when a representative from the developer tried to get into the pub for the first time since early last year.

Police were called but after discovering that the cannabis growers had dangerously tapped into the mains electricity United Utilities were called to make the pub safe.

Local community beat officer Ian Durber said he was shocked at the discovery.

He said: "There have been absolutely no complaints from people who live in this area and I walk past the pub most days and haven't noticed anything.

"No-one has reported anything suspicious."

It is thought that the gang had broken into the building via a fire escape.

Resident Terri Longden, 21, of St Hubert's Road, said: "I saw all of the police but I didn't expect it would be anything like a drugs factory.

"It is a really big shock, I've not seen anything going on there."

Drugs factories run by Vietnamese gangs have been found across East Lancashire in the past year including at a house near Turf Moor in Burnley and a premises in John Street in Accrington.

Sgt Bury said police are keen to speak to anyone who has seen anything suspicious going on at the pub.

Anyone with any information can call 0845 1 253545.