By Dan Shapley
On a day when the pet food recall due to melamine-tainted wheat gluten was expanded yet again, the Food and Drug Administration said it had received as many as 8,500 complaints from pet owners who fear their pets' deaths may have been caused by the bad food. The FDA is continuing its investigation here and in China, where the bad gluten originated. The latest recall wasn't anticipated by manufacturers, who found that some common ingredients had been manufactured in the same plants as brands that used tainted ingredients. The incident highlighted yet again the complexity of the food system, and how little the average American knows - or can know - about the origins of processed foods.