A CANNABIS factory with tens of thousands of pounds worth of plants was uncovered by police today.

Police found 284 plants - potentially worth more than £100,000 - after smashing down the front door at the house in Trafford Road, Headington, Oxford, and believe the 'factory' has been running for months.

Eleven police officers and ten police community support officers arrived at the property at about 11am.

Staff from Southern Electric went in first to disconnect the electricity supply and make the building safe.

Police found all four bedrooms full of cannabis plants at different stages of growth, with one containing young plants and used as a nursery. Another room had been used to harvest the plants and was full of soil.

The windows were taped up with white canvas, while ventilation systems, lights and heaters were all set up.

More than 18 factories have been found in the city this year.

Many have been linked to organised gangs renting houses and using illegal immigrants from Vietnam as 'gardeners'.

PC Rob Fisher said: "There's at least 30 to 40 plants in each room. It's hard to say how long it's been here. They do go in cycles of growth. This could be the first batch or it could be the last of several batches.

"The lights have orange heat lamps as well. They are giving out very intense light to force growth.

"It was like walking into the sun, it was really hot."

Mr Fisher added police would send at least one plant from each room to forensic laboratories to establish their strength and street value.

He warned people to be on the look-out for signs of similar cannabis factories - including strange smells, visitors coming and going at odd times and no frost or snow lying on the roof during cold weather.

A spokesman for Southern Electric said 53 lamps each with 600 watt bulbs were found. He said the electricity had been set up to bypass the meter - which could have meant a loss to his firm of about £17,000 a year.

Neighbour Janet Roberts, 73, said: "I was at the window and then suddenly from everywhere came police in vans.

"There was no escape route. There were one or two guys with helmets and truncheons. I have never seen so many police."

Another neighbour, who asked not to be named, added: "It doesn't surprise me at all. You could smell marijuana when you walked down here. We spoke to police about it."

No arrests have been made. Anyone with information can call police on 08458 505505.