Six men have been arrested in the Netherlands following the discovery of seven shipping containers converted into cells and torture chambers.
The containers were located in Wouwse Plantage, south of Rotterdam, after French police cracked encrypted phones used by criminals.
Dutch police said the containers were found before they were used, and potential victims were now in hiding.
Inside the containers was a dentist chair with straps and handcuffs.
Police also found a building in Rotterdam, which they believe was another criminal base.
The suspects were arrested on 22 June following a Franco-Dutch operation to infiltrate the EncroChat encrypted phone system.
Police intercepted millions of messages including that of one of the suspects, a 40-year-old man from The Hague. Investigators were able to access his contacts via an Encrochat phone.
After locating the containers in April in Wouwse Plantage, near the Belgian border, police put the area under observation and found that multiple men were working on them almost every day. When the containers were almost finished, investigators decided to intervene.
A video posted online by police shows officers arresting the suspects and also entering the containers.
Officers found handcuffs attached to the floors and ceilings of the structures, which had also been soundproofed.
In one container, they also discovered police clothing and bulletproof vests. In another, they located pruning shears, scalpels and balaclavas.
Two of the suspects have also been detained for possession of weapons.
The arrests are among 800 made across Europe after EncroChat messages were intercepted and decoded.
What was EncroChat?
EncroChat, which has now been taken down, was based in France and had an estimated 60,000 subscribers.
It operated on customised Android phones and, according to its website, provided "worry-free secure communications".
Customers were able to access features such as self-destructing messages, which deleted from the recipient's device after a certain amount of time.
The system also had a panic wipe, which meant all data could be removed from the device by entering a four-digit code from the lock-screen.
Gangs are believed to have used the devices to plot attacks on rival groups, plan ways of enforcing drug debts and arrange for money to be laundered. Threats detailed on the site included acid attacks and chopping off limbs.