Melamine is found in the kidneys and urine of dead cats and in the food they eat. However, melamine cannot alone be the cause of illness and death, as melamine is a relatively non-toxic substance. The Food and Drug Administration is studying melamine-related compounds like cyanuric acid, also found in pet foods.  The combination of melamine and cyanuric acid appears to be more toxic than either substance alone. When these two substances interact, they form crystals in the urine and kidney tissue, leading to kidney failure. With advanced forensics, the FDA continues to study the interactions of melamine and related compounds to find the cause of pet illness and death.