The Chinese part of the poisoned pet food story

How did the Chinese factory that produced the poisoned wheat protein powder and killed pets in the States destroy the evidence?
In the beginning of May when the joint investigation team of officials from FDA and AQSIQ (General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China) came to Wuxi Jiangsu to investigate the factory that produced wheat protein powder, the source of poisoned pet food, they found the most important evidence has already been destroyed.
What happened?
Today I read the newest issue of Caijing Magazine and find:
In the middle of April, Li Jun Mao, the manager of An Yin-the company that sold the material for pet food-moved all the machines and wheat? to another village with more than ten tricycles. Each worker who worked for the movement got several hundreds RMB (about $50). These machines and wheat protein powder were moved to another place then.
At the same time, Mao tore down a row of plants in the factory and moved all the ruins. Then he dug out the soil in the ground in case any chemical ? maybe found by testing the soil.
Before the movement, Mao claimed his company had never export wheat protein powder to the States in an interview.
It took Mao several days to do all the things. Both the county government and the police station of the town close to his factory did nothing to stop him.
Ironically, Anyin, the name of the factory also Mao’s nickname_means ”safe camp”.
Then the central government launched a food safety crisis public relation campaign and set a rule that the exported pet food should be checked to see if it has melamin. But what about the pet food sold in China and other goods?