ALL OF THE UNDERGROUND BUNKERS ARE FOR ORGAN HARVESTING.
The temp stability enables refrigeration costs to be kept extremely low and it is hard to see what is going on in there. Anywhere you see bunkers or caves THERE IS ORGAN HARVESTING GOING ON.
Please consider notables for this. Maybe its too dark for everyone though. Anyways why utilize bunkers? If you engage in human trafficking I don't know how much worse the punishment could be than for simple sex slavery, but I imagine the increase in pay makes it worth while. Think logically: what is the most common use of bunkers? Temp stability and refrigeration.