XINGTAI, China (AP) — A Chinese court has sentenced three fentanyl traffickers in a case that was a culmination of a rare collaboration between Chinese and U.S. law enforcement to crack down on global networks that manufacture and distribute lethal synthetic opioids.

Liu Yong was sentenced to death with a two-year reprieve, while Jiang Junhua and Wang Fengxi were sentenced to life in prison Thursday.

Working off a 2017 tip from the U.S. Department of Homeland Security, Chinese police busted a drug ring based in the northern Chinese city of Xingtai that shipped millions of doses of synthetic drugs to the U.S. and other countries from a gritty clandestine laboratory.

U.S. officials say China's vast chemicals industry is the main source of illicit fentanyl. Chinese officials deny that.