Tetrodotoxin. One of the most poisonous substances known, and VERY hard to detect, I understand. Fugu, they call it in Japan. They play a kind of gastronomic Russian Roulette with it there.

The chinese workers I worked with once did not respond well to authoritarian orders and attitude, insofar as they would diligently do exactly what they were told to do, even when they knew it was wrong. When you asked them to tell you if they thought something was amiss, they were brilliant employees. I was QC/QA, and asked them, and listened carefully to them. Even when I moved to a different part of the plant, they would come looking for me for arbitration.

I'll bet the problem is something of this nature. Poor management.