On a dusty industrial lot in northern Hong Kong, a group of travelers sheltered in the shade away from the pressing July heat, packing old cloth bags and backpacks with Styrofoam to protect a more precious cargo: smuggled meat.

Crowded amid the warehouses of Sheung Shui, a remote suburb near the mainland border, the group of around 40 are about to take frozen Brazilian beef into China to feed a growing demand for meat that is unsated by local produce or approved imports.

The part-time smugglers, known as "feet" within the trade, are part of an underground industry that has boomed since Beijing launched a crackdown on meat smuggling last year.