POLICE say they are determined to track down a Teesside crime lord following the arrest of 11 people and the discovery of a drugs factory.

Officers have recovered an estimated 10,000 cannabis plants, with a street value of between £250,000 and £500,000, after raiding a supposedly empty building in Middlesbrough - the former headquarters of the town's probation service.

Police say the raid revealed a "highly effective, industrial-scale'' cannabis farm.

Chief Inspector Gary Stephenson of Cleveland Police told The Northern Echo last night: "A lot of tentacles will lead out from this. We are following the threads back to see who we find.

"Someone, somewhere has a lot of interest in this project. We want to get the main players, the people who are financing this and have a significant financial interest and stake in this.''

He added: "We will have kicked a hole in someone's finances as a consequence of this raid. This in itself may cause some people to break cover. They must owe a lot of people an awful lot of money.''

Officers found specialist lighting - with the mains electricity bypassed - other equipment and chemicals.

The 20 rooms of the seemingly derelict building each held about 500 plants, from seedlings to mature plants.

"It's like a conveyor belt process,'' Chief Insp Stephenson said.

Three men, aged 34, 42 and 49, were arrested at the scene, at the Douglas Street "farm'', for offences including the unlawful production and supply of controlled drugs.

The trio are thought to be Vietnamese and to have secretly lodged in the derelict building for a number of weeks, never moving outside the building. Three others are possibly Iraqis and five British-born Asians.

They were arrested for offences ranging from money laundering, being concerned in the production and supply of controlled drugs and immigration offences.

Immigration officers have joined in the investigations and Cleveland Police are calling in interpreters.

Chief Insp Stephenson paid glowing tribute to the officers who took part in the raids.

"They all did a perfect job, and the operation was only a success because of their professionalism.'