Tests on 19 of 20 chicken houses in the US state of Delaware surrounding the farm where bird flu was discovered showed no signs of further infections, state health officials announced Monday.

The tests were conducted after some chickens on a farm in Kent County, Delaware, were found to have contracted the disease.

State authorities have since ordered the slaughter of 12,000 chickens at the farm and claimed that the H7 virus found there is different from the H5N1 strain now spreading in some Asian countries and does not harm people.

Last year in the Netherlands, a bird flu strain known as H7N7 infected more than 80 people and caused one death, but state officials said the virus found in Delaware is probably a different subtype.

A final determination on the exact strain of the flu will be available shortly, but officials said they expected it to be the low-risk H7N2, which has circulated in the live bird markets in New York City.

The affected Delaware flock was being raised for sale in New York City live bird markets and had come into contact with live birds there, officials said.

After the findings, Japan, Poland, South Korea, Singapore, Malaysia, Mexico and Russia have decided to temporarily ban imports of poultry products from the United States or the state of Delaware.

Delaware governor Ruth Ann Minner said she plans to ask federal officials to appeal to international governments to lift bans on US chickens after the latest discovery of bird flu cases.

"Any banning of poultry imports at this point is probably an overreaction," Minner was quote by The News Journal, a local Delaware newspapers, as saying on Monday.

"This was a small noncommercial flock and there is no evidence of impact yet on our broiler industry," she said.

The chicken industry is the largest agricultural business on the Delmarva peninsula, which consists of Delaware and parts of Maryland and Virginia.

Nearly 577 million meat chickens were produced on Delmarva in 2003, according to figures released by the Delmarva Poultry Industry. Chicken industry in the region now employs more than 14, 000 people and produces about 8 percent of all meat chickens in the US.