A drugs laboratory capable of producing £10m of amphetamine a month has been uncovered during a police raid.
The "large-scale" operation was found in outbuildings on Ullenhall Lane near Redditch, Worcestershire.
The investigation began after text messages were obtained by French police during the penetration of the encrypted phone network Encrochat last year.
Vats and sacks of ingredients were found in the lab, which is currently too hazardous for police to enter.
Five people have been arrested in the joint operation between the National Crime Agency (NCA) and Warwickshire Police on Tuesday.
Firefighters and a chemicals expert were drafted in to assist with the raid.
Footage of the inside of the building has been sent to scientific experts for analysis.
Peter Stevens, branch commander at the NCA, said conducting the raid on the "semi-rural" site had taken weeks of meticulous planning.
"The laboratory will make illicit amphetamine, it is a class B drug, and will be sold on the market for approximately £2,000 per kilo, wholesale price," he said.
"It involves a number of different chemicals, all very volatile and dangerous chemicals, as well as some quite specific and sophisticated scientific apparatus and equipment.
"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."
Assistant Chief Constable Alex Franklin Smith, from Warwickshire Police, said he is confident the operation will have a "huge" impact on the organised criminal gangs involved.
"Such an operation taking place in such a quiet, rural location will no doubt have caused some concerns for people in the area," he said.
"Our officers will be working with people in the local community in the coming days to provide reassurance."
Police raided two other properties in Chalfont St Giles, Buckinghamshire, and Quinton, Birmingham, in connection with an investigation into an organised crime network.
Warwickshire Police said two men, aged 40 and 60, were arrested in Buckinghamshire. A third man, aged 50, suspected of operating the lab, was apprehended at his home in Quinton.
While a man aged 36 and a woman aged 28 were arrested at a building on the site.
All five remain in custody where they are being interviewed, the force added.
Officers said searches of the farm buildings are ongoing, with support from specialist teams from West Midlands Police, West Midlands Fire Service and West Midlands Ambulance Service.
This operation is the latest in a string of cases which have resulted from the penetration of Encrochat.
French police obtained the messages of 9,000 British people using the service, and the NCA said the vast majority were using it for criminal purposes.
More than 1,500 people have been arrested in Operation Venetic, the British effort to analyse criminality using the messages.
Update: This story has been amended to remove references to methamphetamine following updated information provided by the NCA.