Police found a massive underground cannabis farm after uncovering a secret trapdoor in the floor of a disused Leeds warehouse.
The hatch was buried beneath rubbish in the empty building on Town Street, Stanningley.
After climbing through a 2ft by 2ft space, officers found a sophisticated growing operation and nearly 600 plants.
The discovery came after tip-offs from the public.
Insp Mark Wheeler, who leads the Armley, Bramley and Stanningley neighbourhood policing team, said: “This was an unusual incident in terms of the concealed location of the cannabis farm, but it does demonstrate the value of community intelligence and how effective the public can be in reporting suspicious activity.”
Police went to the site on Saturday in response to information about suspicious activity at the warehouse.
The trapdoor was found beneath piles of waste and empty boxes.
Once underground, they found the mains power supply had been hacked into to fuel a large-scale heating and water system.
As well as 578 plants, a bin liner containing dried cannabis buds was seized and destroyed.
Two local men, aged 41 and 50, were arrested on suspicion of producing class B drugs and stealing electricity.
Following a further search of a house in Stanningley, a 39-year-old woman and an 18-year-old man were arrested on suspicion of production.
Financial documents were also seized.
All four arrested people have been released on bail.
Insp Wheeler added: “With almost 600 cannabis plants destroyed, this police activity will have a significant impact on the local drug market.
“Cannabis factories are used by organised criminals to fund a number of other illegal activities that are often perpetrated on those living and working in the same area.
“The combination of high amounts of electricity and water can also be extremely dangerous, particularly for those living close by.”