Five people have been arrested after a suspected £10m amphetamine laboratory was uncovered during a police raid.
Officers discovered the “industrial-scale” operation in farm buildings near Redditch, Worcestershire, on Tuesday.
Vats and sacks of ingredients were found inside the lab, which is too dangerous for police to enter, according to the BBC.
Investigators believe the operation was capable of producing about one tonne of amphetamine per month - worth £2m at wholesale and up to £10m at street level - which was then distributed to criminals throughout the country.
Members of the organised crime group believed to be running the drugs operation - two men aged 40 and 60 - were arrested in Chalfont St Giles in Buckinghamshire.
A third man, aged 50, from Quinton, Birmingham - suspected of operating the lab - was detained at his home address.
Two other individuals - a 36-year-old man and a 28-year-old woman - were arrested at a building on the site in Ullenhall Lane.
All five are still in custody being interviewed.
Peter Stevens, branch commander at the NCA, said the discovery was “rare” because the process of making amphetamine involves a number of “very volatile and dangerous” chemicals, specialist equipment and someone who knows how to use them.
He told the BBC: “It takes someone with a very good knowledge of those chemicals and the processes required to produce the amphetamine, which is why it is rare for us to encounter it as it needs a crime group that is able to access the chemicals, able to access the equipment and then have someone that can essentially cook the chemicals.
"Once it is cooked, they can then distribute it to other crime groups in the UK, as this crime group has done."
He added that amphetamine, a class B drug, could be sold on the market for about £2,000 per kilo at “wholesale price”.
Assistant Chief Constable Alex Franklin Smith, from Warwickshire Police, said: “We are absolutely committed to tackling the drugs trade and protecting the people of Warwickshire from all the harms it brings.
“This operation once again sends out the message that this offending will not be tolerated in our county.
“Such an operation taking place in such a quiet, rural location will no doubt have caused some concerns for people in the area.
“Our officers will be working with people in the local community in the coming days to provide reassurance.”
Searches of the farm buildings are ongoing, with support from specialist teams from West Midlands Police, West Midlands Fire Service and the West Midlands Ambulance Service.
The sting is the latest in a series of raids targeting organised crime gangs since law enforcement agencies gained access to EncroChat last year.
The secretive communications network was used on bespoke mobile phones designed to be secure against police infiltration and examination.
But in April 2020, an international team cracked its encryption, started spying on users and harvesting their data as they carried on unawares.
The platform was infiltrated by agencies in France and the Netherlands, and shared via Europol to partners including the UK.
Since then, hundreds of arrests have been made across the UK, including “high-value targets” and “iconic” fugitives who have previously evaded justice.