No chicken feed tainted with melamine was found in Arkansas during a recent battery of tests, state agriculture and health officials said Monday.

Springdale-based Tyson Foods Inc., which contracts with chicken growers in many states, said the industrial chemical was not discovered in its chicken feed, either.

The news came hours after the U. S. government released for slaughter 20 million chickens in several states that were held last week for health safety testing.

Richard Bell, the Arkansas secretary of agriculture, and George Pat Badley, the state veterinarian, confirmed in discussions with the U. S. Department of Agriculture that no melamine was detected in the state’s chicken feed.

“The latest that we had is that the USDA is still checking feed samples, but at this time there is no knowledge of any exposure to Arkansas poultry at all,” Badley said in a Monday telephone interview from his office in Little Rock. Arkansas produced about 1. 2 billion chickens in 2006.

Melamine, a chemical found in plastics and pesticides and not approved for use in pet or humanfood in the U. S., contaminated pet food that either sickened or killed an unknown number of dogs and cats.

Scraps left over from the manufacture of that pet food were sold for use in animal feed before the pet food was known to be tainted and recalled from store shelves.

“To date, tests of Tyson poultry feed have not discovered the presence of melamine and our poultry plants are operating normally,” Tyson spokesman Gary Mickelson said Monday in an e-mail to the Arkansas Democrat-Gazette.

On Friday, the USDA said 20 million chickens were being held while the government determined whether the birds that consumed the melamine-laced feed were safe to eat. Those chickens were released Monday for slaughter after the USDA and other government agencies said humans were not at risk.

USDA testing found that melamine in the birds was so diluted that any human exposure from the meat or eggs of the animals would be thousands of times lower than the level considered safe, U. S. Agriculture Secretary Mike Johanns said Monday during comments to the Organic Trade Association.

“We literally found that the dilution is so minute, in fact in some cases you can’t even test and find melamine anymore in that product,” he said.

People who ate large amounts of contaminated pork, chicken and eggs likely would be exposed to contamination at levels 18, 000 to 30, 000 times below that considered safe, the USDA said.

The chickens were on farms in several states, USDA spokesman Keith Williams said in an interview. The agencies did not specify the locations or the companies involved.

About 6, 000 hogs still were being held in six states Monday for further testing. The animals, who have been held since late April, ate feed that either tested positive for contamination or was no longer available to test.

Johanns said he hopes to announce the release of those animals by the weekend.

USDA spokesman Terri Teuber said the government is confident the hogs and remaining chickens are safe to eat, but the USDA wanted more testing before releasing them into the food chain.

In a conference call last week to Wall Street analysts, Chief Executive Officer Richard Bond said 195 hogs that ate melamine-tainted feed went to a Tyson Foods processing plant in Nebraska. Bond was quick to point out that the USDA found no reason to believe humans were at risk.

In 2006, Tyson sold about $ 3 billion of pork, which is the meat producer’s smallest segment. The nation’s largest hog and pork producer, Smithfield, Va.-based Smithfield Foods, had $ 11 billion in annual revenues in 2006.

Melamine has been found in wheat gluten and rice protein imported from China.

Companies including Canada’s Menu Foods Ltd. have recalled more than 100 brands of pet food as U. S. and Chinese investigators probe for the source of the outbreak.

The government initially said about 5 percent of feed used at some smaller chicken production operations was contaminated. But Monday, Johanns said some larger producers also were affected. He did not name the producers.

U. S. investigators are currently in China working with officials there to trace the source of the melamine. The FDA said Thursday that testing of vegetable protein imports from China suggests the problem may be limited to two Chinese suppliers already implicated.