A flock of about 240,000 chickens owned by Tyson Foods Inc in Kentucky tested positive for a highly lethal form of bird flu, government officials and the company said on Monday, widening an outbreak that threatens the U.S. poultry industry.

Infections in the chickens being raised for meat triggered more restrictions on U.S. exports, with China blocking poultry products from Kentucky. Last week, buyers like China and Korea limited poultry purchases from Indiana due to an outbreak at a commercial turkey farm there.

The broiler chickens in Fulton County, Kentucky, located near the border with Tennessee, were infected with the same H5N1 strain of highly pathogenic avian flu as the turkeys in Indiana, Kentucky officials said.

They said it is Kentucky's first outbreak of the highly lethal bird flu, which killed more than 50 million U.S. chickens and turkeys in 2015.

Birds from the infected flock will be culled and will not enter the food system, state officials said.

Tyson Foods is working with government authorities to prevent the disease from spreading and is heightening safety measures at other local farms, spokesman Gary Mickelson said.

The outbreak is not expected to lower overall chicken production levels because thousands of farms raise chickens for Tyson, he said. Mickelson added that Tyson Foods' chicken products are safe to eat.

On Tuesday, Kentucky officials expect final test results for a separate suspected outbreak among turkeys in Webster County, Kentucky.

The disease was also detected in a backyard flock of birds in Fauquier County, Virginia, that have already been culled, the U.S. Department of Agriculture said. The cases do not present an immediate public health concern, the agency said.

Wild birds are thought to be spreading the virus, after dozens tested positive along the U.S. East Coast.

The United States is the world's largest producer and second-largest exporter of poultry meat, according to the U.S. government. Kentucky said it is the seventh biggest chicken-meat producing state. Almost 18% of U.S. poultry production is exported, and the industry is a major user of feed grains.

The disease is hitting the market as poultry supplies are down due to strong demand and labor shortages at meat plants during to the COVID-19 pandemic. Government data showed U.S. frozen chicken supplies were down 14% from a year ago at the end of December while turkey inventories were down 23%.