Story Highlights• The FDA will test imported ingredients for contamination
• Wheat gluten, corn gluten, cornmeal, rice bran, rice protein to be checked
• Hogs on farms in three U.S. states test positive for melamine
• No contamination has been found in human food, the FDA says
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NEW YORK (CNN) -- For the time, the Food and Drug Administration said it will test ingredients imported for use in the human food supply in connection with the nationwide pet food recall that has killed, by some estimates, thousands of pets.
"The FDA wants to take a proactive stance right now and ask, 'Could this be in other concentrates that may be getting into other pet food or human food?' " asked Dr. David Acheson, chief medical officer for the FDA's Center of Food Safety and Applied Nutrition.
"Right now, there's no indication that that is happening, but we know there are other types of protein concentrates that come into the United States, and we think in the interest of public health, that we should get out there and look for it," Acheson said Wednesday.
Families victimized by tainted spinach and peanut butter put a human face Tuesday on a recent string of high-profile outbreaks of foodborne illness, urging lawmakers to strengthen federal oversight of the nation's food supply.
A poultry farm in Missouri also is under investigation, federal officials said.
Wheat gluten, corn gluten, cornmeal, rice bran and rice protein are among the imported products being tested in both the animal and human food supply. (Watch suggestions for improving U.S. food inspections )
"I want to emphasize that this is a proactive step," Acheson said.
The comprehensive testing will begin at the end of the week and focus on public awareness and checking of samples, according to Acheson.
The FDA said hog farms in California, North Carolina and South Carolina have been quarantined after tests found melamine in the swine's urine. Owners of a hog farm in Ohio also are working with the FDA.
Hogs from farms in New York and Utah also have been placed on hold for distribution, but testing has yet to confirm the presence of melamine in those animals, federal officials said.
The FDA has officially tallied 16 animal deaths related to the wheat gluten-pet food recall, but other organizations have put the death toll in the thousands. Cats seem to be more susceptible; one of the confirmed deaths was a dog.
The recall started March 15 with Menu Foods Inc., a Canadian company that makes a long list of popular pet food brands, including Eukanuba, Iams and Wal-Mart's Special Kitty. (Check for pet food on the FDA's list)
Investigators from the Cornell University's College of Veterinary Medicine found those products contained wheat gluten contaminated with melamine, a plastic compound used in fertilizer in some countries but banned for that purpose in the United States.
Little research has been done to show that melamine causes kidney failure, but its association with the recent pet deaths is undeniable, the FDA said.
Signs of kidney failure in animals include vomiting, lethargy and loss of appetite, the veterinary school noted.
The contaminated wheat gluten, and later other ingredients, came from a single distributor in China, FDA investigators found.
Now, 80 food products for dogs and 56 for cats -- including such major brands as Alpo, Mighty Dog and Hill's Science Diet -- have been recalled because they contain ingredients that could be tainted.
CNN's Richard Davis and Katy Byron contributed to this report.
Cans of pet food that were pulled from store shelves sit in a storage area last month at a Petco in Miami, Florida.
Sources: OSHA, CDC