According to an article appeared in the Wall Street Journal, "protein powder" of uncertain origin has been used as a cheap way to fool dairy companies' quality checks. Farmers used the "protein powder" to fool the dairy companies' about the fat contents, protein contents and freshness. The article has listed down all possible ingredients of the "protein powder" and one of the ingredient is of course melamine.
According to the article, the underlying problems remains i.e. flaws in farming methods and relatively lax supervision. Flaws in farming methods is due to lack of capital and know-how to adhere to good dairy-farming practices.