A huge cannabis factory covering three floors of a derelict tower block scheduled for demolition has been found in the middle of a housing estate.

Police had to get through an internal steel-barred door, reinforced with a metal grille, and an industrial-sized padlock before discovering the “sophisticated” operation.

Inside, officers found plants with an estimated street value of £500,000, along with living quarters and stocks of food for those tending the operation.

Door
Officers discovered a large-scale cannabis-growing operation behind a reinforced internal door (West Midlands Police/PA)

A loading winch had also been fitted into one of the block’s empty lift shafts.

Winch
The winch had been fitted into an open lift shaft (West Midlands Police/PA)

The 20-storey block, Warstone Tower, in Bromford Drive, Birmingham, has been earmarked by the city council for demolition and has been empty for some time.

West Midlands Police’s cannabis team found plants growing on the 16th floor but equipment sprawled across the 15th and 17th floors, covering 31 rooms in total.

One floor had been given over to growing (West Midlands Police/PA)

Electricity was being abstracted, while another room had containers holding gallons of water with a pumping system installed, along with ducting for the air conditioning system.

The growers had also knocked holes in the floors, ceilings and walls to run hundreds of feet of piping and cable.

A web of cables, pipes and ducting had been run throughout the site (West Midlands Police/PA)

Reams of wiring had also been run up the internal staircases.

Further inside the warren of rooms, beds with mattresses, duvets and pillow cases had been brought in, along with food provisions including a box of tomatoes.

Food
The operation had been well-provisioned with food, including vegetables (West Midlands Police/PA)

Officers arrived after a member of the public called police on January 24.

Five men were arrested at the scene on suspicion of cannabis cultivation.

Beds
Beds and mattresses were also discovered (West Midlands Police/PA)

Detective Inspector Jim Church, of West Midlands Police’s CID, said: “This is a sophisticated, organised crime operation that has clearly been running for some time, but which we’ve now been able to dismantle.

“We’ll be working throughout the day to establish the full scale of it and make the property safe.”

Equipment
Police officers needed specialist equipment to navigate the sprawling site, safely. (West Midlands Police/PA)

Cllr Majid Mahmood, who represents the ward, said the tower had been due to be pulled down after a neighbouring derelict block had been successfully demolished, last year.

The work is part of a housing redevelopment plan for the area.

But concerns over debris coming down on a nearby school had pushed back the date to August this year, when work would happen during the summer holidays.

Water
Gallons of water was stored on-site. (West Midlands Police/PA)

He said: “Questions need to be asked about how those people were so brazen, living there and running a cannabis farm, when you’ve got shops nearby and a church, so you’ve got a lot of footfall.

“I think a lot of people might have thought they  were the (demolition) contractors, coming and going, but with the stench of the plants that must have been coming from there, I’d have thought someone would have noticed.”

He added: “The only silver lining is because this has now happened, it means the city council will secure the property.”