By Agence France-Presse Spanish police said Thursday they have broken up a Chinese gang that allegedly forced illegal migrants to work in "conditions of semi-slavery" to produce marijuana for export across Europe. The gang is suspected of growing marijuana in warehouses rented in industrial areas, mainly in the eastern region of Valencia. It was shipped to other EU nations, especially Britain and the Netherlands, via private courier firms in small packages labelled as containing clothes, police said in a statement. Thirty-six Chinese and Vietnamese men who had been forced by the gang to work round-the-clock in the warehouses in "degrading conditions of semi-slavery" were freed during the operation, which followed an eight-month investigation, the police statement added. "Living conditions inside the warehouses were very precarious, unhealthy and with poor hygiene," police said. "Some of the victims said they were not allowed out on the streets and could not communicate with the outside; they only received food to be able to continue working like slaves." Police estimate the gang had exported around 4.2 tonnes of marijuana since the beginning of 2018. Officers also freed 13 Chinese women who the gang is believed to have forced to work as prostitutes. Police arrested a total of 81 people as part of the operation. The vast majority were Chinese nationals but there were also a few British and Vietnamese nationals among those detained, a police spokeswoman said. The authorities dismantled 19 warehouses used by the gang and seized over 22,000 marijuana plants weighing some 3.4 tonnes, police said.