Where does the melamine come from ... how would it be added to dairy products? Is it a natural contaminate from cows feeding on melamine laced feed and why/from where is this derived??
Melamine was added to milk powder in China for the same reason it was added to Chinese wheat gluten used in pet food last year -- to boost the nitrogen content to appear to contain more protein.
Instead of measuring protein for quality control, simpler tests to assess nitrogen content were performed. Melamine is relatively high in nitrogen. Melamine is only slightly soluble, so it's easier to add in powder form.
I would guess that the melamine was added to hide the fact that the ersatz milk powder and baby formula (and wheat gluten) were diluted with rice, flour, gypsum, or other powders that reduced the the protein content.
I'm surprised the Chinese haven't tried to add 15-15-15 fertilizer to food for the nitrogen and minerals....