HANOI (AFP) —Police in Vietnam busted the country’s biggest synthetic drug factory, seizing 1.4 tons of ketamine in the coastal tourist city of Nha Trang, the government said.

A six-month operation to uncover the drug ring culminated last Saturday when 200 officers raided three linked facilities in the southern city and arrested 11 people, including a Taiwanese national who was the alleged mastermind.

“This is the largest synthetic drug manufacturing facility ever dismantled in Vietnam,” said Nguyen Van Vien, director of the department of drug-related crime investigation, according to a statement published on the government’s official news portal on Wednesday.

“It featured ‘an exceptionally large-scale, modern production line, with advanced technology,’” he said.

Among those arrested were four Vietnamese nationals, four Chinese citizens and three Taiwanese, including the 51-year-old alleged ringleader Chang Chun Ming, who police had monitored since his entry into Vietnam last August with a large shipment of glass tubes, the news portal said.

Chang rented a 1,300-square meter plot of land in November in a remote area of Nha Trang, a city popular with Chinese tourists, and allegedly recruited among others two fellow Taiwanese nationals with expertise in drug manufacturing.

Activities were mainly conducted at night and the semi-finished product was later moved to another facility for purification.

The drugs produced had extremely high purity but none had yet been distributed or sold in Vietnam or abroad, the government statement cited police as saying.

A Vietnamese court sentenced 27 people to death in December after finding them guilty of trafficking more than 600 kilograms of narcotics including heroin, ketamine and methamphetamine.