A Michigan State University survey says more than 300 dogs and cats may have died earlier this year as a result of eating contaminated pet food.
The study says the deaths likely were linked to melamine and cyanuric acid.
The two food contaminants are relatively harmless alone but turned deadly when they were combined by pet food manufacturers.
The melamine was in contaminated pet food ingredients sent from China.
Michigan State found that 235 cats and 112 dogs were sickened by the contaminated pet food.
The largest number of cases occurred in Texas, Illinois and Michigan.