Melamine is banned in human and animal food in the US.
It is also banned for use as a fertilizer, as it is in some parts of the world.
Melamine can sometimes be added to the grain products to make them appear higher in protein than they are.
The USDA said that meat from swine exposed melamine does not accumulate the chemical, which is filtered out of the body by the action of the kidneys.
Testing results support conclusions reached by a human health risk assessment that there is a very low risk of human illness from the consumption of meat from animals exposed to the feed in question, the USDA said.
The USDS said animals known to have eaten this feed appear healthy, and this will be confirmed by Food Safety Inspection Service (FSIS) inspections conducted prior to meat and poultry processing.
About 56,000 swine consumed feed containing melamine and were held on farms in across US states.
FDA and USDA are in the process of identifying scientific experts who would be charged with reviewing an updated risk assessment.
They will be asked to provide their views to FDA, to enable the finalizing of a risk assessment within several weeks.
About 80,000 poultry are currently being held at the USDA's request at farms in Indiana while a validated test for detecting melamine in poultry meat is developed.
That test is expected later this week.
The USDA said it will compensate producers for some additional costs incurred as a result of voluntarily holding the animals.
About 100 million swine are processed each year in the US, according to the USDA.
Concerns over melamine were first raised following the discovery of the chemical in pet food imported from China.
Pet food manufacturers have voluntarily recalled more than 100 brands of dog and cat food across the country since 16 March, prompted by reported cases of cats and dogs that developed kidney failure after eating the affected products.
Due to concerns in the US, China has now banned the chemical's presence in ingredients meant for export.