Fentanyl, 50 times more potent than heroin, and related laboratory-crafted drugs have become the No. 1 cause of opioid-related overdose deaths. And rogue chemical companies in China -- operating openly and outside the reach of U.S. authorities -- are the largest single source of the deadly drugs, law enforcement officials say.
"People in labs in China are producing this substance that is killing Americans," Deputy Atty. Gen. Rod Rosenstein said in an interview. "This is a real crisis. The Chinese government has the ability to stop this if they want to. We believe they should want to do that."