Consumers face little risk from eating pork, chicken and eggs from farm animals that ate feed mixed with pet food scraps contaminated by an industrial chemical, government scientists said Monday.

Mixing in material contaminated at low levels diluted it such that humans who eat the animals won't be harmed, the scientists said.

The government also recommended lifting holds placed on some pigs and chickens after their feed tested negative for the chemical, melamine, and related compounds. Those animals may be slaughtered and enter the food supply, the Agriculture Department and Food and Drug Administration said.

Other animals, including some that ate feed that has tested positive for contamination, are likely to be held for another week pending completion of an assessment of the overall risk of the chemicals to animal health.

Melamine, used to make plastics, and the related compounds contaminated pet food that either sickened or killed an unknown number of dogs and cats. Scraps left over from the manufacture of that dog and cat food was sold for use in animal feed before the pet food was known to be tainted and recalled from store shelves.

Holds were placed on hogs and poultry while officials studied the extent of the problem as well as its potential risk to both human and animal health.

Since the pet food scraps made up only a small amount of the rations fed the farm animals, they appear to have been exposed to smaller amounts of melamine than was the case with cats and dogs, officials said. Even pigs and chickens known to have eaten contaminated feed appear to be healthy, the USDA and FDA said.

For people who ate large amounts of contaminated pork, chicken and eggs, they likely would be exposed to contamination at levels 18,000 to 30,000 times lower than that considered safe.

Even under the most extreme scenario, the potential human exposure to melamine was well below any level of public health concern, the USDA and FDA said. In that worst-case scenario, government scientists assumed all the solid food a person ate in a day was contaminated with melamine at levels seen in animals fed contaminated feed; that potential exposure was still about 2,500 times lower than the dose considered safe.

Since March 16, more than 100 brands of pet food have been recalled because they were contaminated with melamine.