A drug syndicate that targeted migrant workers in Nantou County in central Taiwan has been busted and police have arrested a Thai man alleged to be the gang’s ringleader.

In May this year, the Nantou County Police Bureau received intelligence reports alleging some Thai blue-collar workers in Nangang Industrial Park were using amphetamines to get high and keep them awake so they could work overtime and earn more money, the Liberty Times reported.

After a three-month investigation, police found that more than 52 migrant workers from Thailand, Indonesia and Vietnam in 16 factories in the industrial park had been using amphetamines supplied by a drug syndicate.

Officers arrested the alleged Thai ringleader on Friday and 11 others were also arrested for distributing the illicit substances.

Nantou police are expecting more arrests as preliminary investigations suggest the syndicate had at least four layers of members involved in trafficking and distributing.