Approximately 100 food companies were forced to recall millions of units of pet food in March of 2007 when several hundred dogs and cats died from kidney failure. The pet food was determined to contain tainted wheat gluten. Various studies from laboratories indicate the presence of other harmful chemicals in different levels, but most fail to pinpoint the exact culprit, but the prime candidate is melamine, a chemical used in plastics, kitchen products, and pesticides, and is a known toxin.