Police in central China recently uncovered a production lab for illicit weight loss drugs discreetly hidden in a four-story building deep in the mountains.

At a press conference on Tuesday, police from Loudi, a city in Hunan province, said that they confiscated nearly a million pills from the house in July and found that they contained sibutramine, a banned and toxic substance that can suppress appetite but also lead to neurological disorders, liver dysfunction, and other serious side effects.

In 2010, the China Food and Drug Administration banned the production, sale, and use of sibutramine.

However, sibutramine’s low production cost has made it hard to keep off the market. One of the four main suspects in the Hunan case, identified only by his surname, Zhang, confessed to police that the cost of producing one pill was less than 0.10 yuan ($0.02), and that he profited between 0.2 and 0.3 yuan from each tablet. An automatic capsule-filling machine confiscated at the house was capable of processing 10,000 pills per hour.

The pills produced in the house were distributed through sales agents on e-commerce platform Taobao and through chat apps. Consumers paid about 10 yuan per tablet.

According to Loudi police, nearly 100,000 boxes of the drugs were sold in at least 20 provinces. Authorities said they are still trying to track down all the boxes, which were sold with different packaging and under different brand names.

In total, the pills the suspects produced were valued at nearly 100 million yuan. In January, police in Suzhou, eastern China, arrested a gang that produced illegal weight loss tablets valued at an estimated 10 million yuan.

Police were able to crack both cases due to tip-offs from Taobao. In December 2016, the platform first reported to Hunan provincial police that they were suspicious of a weight loss product called “Little Green,” sold out of Hunan.

According to the China’s obesity index, released in 2015, as many as 300 million people in the country are overweight, and 46 million are obese. The same report said that nearly 80 percent of people trying to lose weight were below the age of 29.

Editor: Kevin Schoenmakers.

(Header image: Yi Ming/IC)