Thousands of Chinese immigrant laborers suffer abuse and exploitation in a U.S. marijuana underworld dominated by Chinese mafias. A human rights advocate says: “They have not escaped the darkness of China.”

“It is one of the most deplorable parts of what we see in this industry,” said Donnie Anderson, the director of the Oklahoma Bureau of Narcotics, who met with Zeng’s relatives and ordered an investigation.

Cannabis farms have boomed in states that have passed medical and recreational marijuana laws. But when voters in Oklahoma approved a law allowing the cultivation of medical marijuana in 2018, legislators didn’t develop corresponding regulations to protect employees. Oklahoma’s historically weak labor enforcement system leaves the protection of workers largely to the federal government. And the U.S. Department of Labor has limited oversight because marijuana is illegal at the national level.