LITTLE ROCK, Ark. — Tyson Foods Inc., said Monday that 195 hogs sent to a Tyson pork plant in Nebraska may have eaten feed from China that had been treated with the banned chemical melamine, the Associated Press reported.

The company said there is no cause for alarm, but referred questions to federal food inspection authorities, who said over the weekend that even if the hogs had consumed melamine, they would pose no danger to humans.   

Apparently widely practiced in China, the use of melamine in pet food, and the fear it may have been introduced into human food,  have caused distress and uncertainty in the United States since March.

Chinese wheat gluten containing melamine was blamed for a wave of pet deaths in March due to kidney failure. The U.S. Food and Drug Administration investigated, and nearly 100 brands of pet food made with the ingredient were ordered recalled. Adding melamine to food is illegal under American law, and China's government last week said it was banning its use in food products.

Tyson spokesman Gary Mickelson said government officials last week inquired about 195 hogs slaughtered early in April at Tyson’s Madison pork plant. 

“They thought the hogs may have consumed feed containing melamine,” Mickelson said by email Monday afternoon.  “However, the government has since told us these hogs are no longer considered a concern and are not being further investigated. “

Asked to elaborate, Mickelson emailed:  “As indicated in our previous e-mail, the hogs were slaughtered at the Madison plant.  For a more specific answer to your other question, we recommend you contact USDA (the Food Safety and Inspection Service.)”

It’s still uncertain, according to USDA, whether the hogs slaughtered at Madison ever ate tainted food. Tyson CEO Dick Bond told the Associated Press earlier there is no indication of harm to humans and that the meat was not recalled.

Over the weekend,  the Department of Agriculture and the Food and Drug Administration said a continuing investigation affirms that the risk to humans from hogs that may have eaten contaminated pet food is very low and that no recall is warranted.

“Based on information currently available, FDA and USDA believe the likelihood of illness after eating pork from swine fed the contaminated product would be very low,” the agencies said.

The government said last week that 345 of 6,000 hogs that may have eaten the food are believed to have been placed on the path to slaughter, but that almost all the rest are still on farms in California, New York and South Carolina.

Those states were told that no meat from any of those hogs can enter the food supply.

“Testing and the joint investigation continue. If any evidence surfaces to indicate there is harm to humans, the appropriate action will be taken,” the agencies said.

Salvaged pet food from companies known or suspected of using the melamine ingredient was shipped to hog farms in several states for use as feed.

The pet food sent to the farms later was discovered to have an ingredient, rice protein concentrate, imported from China that was tainted by the industrial chemical, melamine. Testing also revealed other related and similarly banned compounds, including cyanuric acid.

In China, the mildly toxic chemical melamine is commonly used in animal feed and is even praised by some customers as harmless.

 “Using the proper quantity of melamine will not harm the animals,” said Wang Jianhui, manager of the Kaiyuan Protein Feed company in the northern city of Shijiazhuang. “Our products are very safe, for sure,” Wang added.

Scientists say there is no evidence that people could get sick, but say they know too little about how the chemical reacts with other substances to be sure it is safe.

Usually used to make fertilizer and plastics, melamine has no nutritional value but is rich in nitrogen, which raises the nitrogen level of feed. That can make those products appear to be higher in protein, which can make them more expensive as food for stock animals such as pigs, chickens, and fish, as well as for household pets such as cats and dogs.

James Kapin, a member of the American Chemical Society’s executive committee on health and safety, said testing on rats and mice has shown melamine to be toxic only at extraordinarily high levels.

 Kapin said the process by which pet food is made or, more likely, the metabolic process of the animals that ate the pet food might have morphed the melamine into a different, more lethal compound, which would explain its toxicity at low levels.