The fentanyl funnel: How narcos sneak deadly chemicals through the U.S. by Reuters

The U.S. has become a major transshipment point for Chinese-made chemicals used by Mexico’s cartels to manufacture fentanyl. Narcos have pulled it off by riding a surge in e-commerce that’s flooding U.S. airports with packages.

Some of those boxes contain disguised fentanyl ingredients that are then routed south to Mexican drug labs. A 2016 tweak to U.S. trade legislation helped make it all possible.

This extraordinary feat of explanatory journalism looks in detail at the flow of chemicals used to produce fentanyl.