A Vietnamese man was arrested during the early hours of Sunday in a rural district of southern Tainan, Taiwan, after allegedly running a gambling den that targeted compatriot immigrants and migrant workers.

Police in Gueiren district, Tainan, had received citizens’ complaints regarding an apparent gambling site operating in their neighborhood that catered to immigrants and migrant workers, usually during factory rest hours, China Daily News reported.

Though its clients were reportedly cautious and the location of the den was frequently changed, undercover police officers were able to locate it inside a snack shop at 2am on Sunday.

A Vietnamese man identified as the mastermind running the gambling den was arrested. He later was found to be a runaway migrant worker who no longer had a valid work permit in Taiwan.

An alleged accomplice, a new immigrant who worked as a guard, was also arrested at the same time.

Another 12 men and women, all Vietnamese, were arrested for illegal gambling after being caught playing a Vietnamese dice game, and a grand total of NT$6,000 (US$200) was seized at the scene.