Police in Staffordshire say they have uncovered one of the UK's largest ever cannabis farms during a raid on former chicken barns.

Some 3,100 cannabis plants worth an estimated £1.5m ($2m, €1.7m) were recovered from Three Angels chicken farm in the village of Wheaton Aston on Tuesday (5 December).

Three men were detained at the scene while another three were arrested following a police search of the area.

The suspects, aged between 17 and 44, are from the UK and Albania and slept at the site to manage the mammoth operation, police said.

A spokesman said four of the men have since been released under investigation.

No further action is being taken against the remaining two men, both Albanians, who have been transferred to an immigration centre where they will face possible deportation.

A video tour of the farm, taken by police officers, shows where the men slept adjacent to row upon row of cannabis plants.

Inspector Richard Meaden, South Staffordshire local policing commander, said: "The investigation is at an early stage, however we can confirm that approximately 3,100 cannabis plants were recovered. This estimated value of this crop is estimated to be worth £1.5m.

"This is the largest and most sophisticated cannabis factory I've ever experienced and I am delighted we have been able to take such a large number of drugs off the streets."

The bust came months after three men were jailed for their part in running another vast cannabis farm – this time in a former Cold War nuclear bunker.

Some 4,400 cannabis plants were found at the £2m-a-year underground site in Wiltshire, which was staffed by young Vietnamese workers held in slave-like conditions.

Martin Fillery, 45, Ross Winter, 30, and Plamen Nguyen, 27, all pleaded guilty to conspiracy to produce class B drugs and abstracting electricity to power the drug factory at the decommissioned Ministry of Defence bunker, RGHQ Chilmark.