Connecticut agriculture officials are investigating a possible outbreak of avian influenza at an Eastern Connecticut egg farm that has led to the quarantine of 4.7 million birds.

Michael Darre, a poultry extension specialist and animal science professor at the University of Connecticut, said the apparent outbreak occurred at Kofkoff Egg Farm, which has operations in Bozrah and Lebanon and controls more than 90 percent of the state's egg market.

Connecticut has more chickens per square mile than any state in the nation, according to the Connecticut Farm Bureau.

The apparent outbreak led Japan on Thursday to impose a temporary ban on poultry imports from the United States.

"This is a devastating disease to poultry but zero risk to humans or any mammal," acting Agriculture Commissioner Bruce Gresczyk said.

Gresczyk said samples from the farm have been sent to a diagnostic laboratory in Iowa and results are expected next week. State officials learned of the possible illness last week.

"We have no hard confirmation but we have suspicions," said Gresczyk.

He said the particular strain suspected is considered a low-grade pathogen and in some cases is not fatal to chickens.

Meanwhile, traffic at the farm is strictly limited. Employees must take foot baths before entering the coops and vehicles are being disinfected leaving and entering the property, Gresczyk said.

Several messages seeking comment were left with a Kofkoff farm manager Thursday. The farm produces about 12 million eggs per week.

While Gresczyk would not confirm the name of the farm, he said the disease does not affect eggs and said there are no problems with any of the products the farm has on the market.

It's not the first case of the disease in the state. In 2001, some 16,000 birds had to be destroyed at a farm in Scotland because of an influenza outbreak.

If influenza is confirmed in the most recent case, the state may have to destroy the flock, Gresczyk said.

The egg industry is among the top five agriculture businesses in Connecticut with annual receipts of between $60 million and $100 million.

"It will affect the whole market," said Harvey Polinsky, an egg distributor in Griswold.

Maine and Connecticut are the top two egg-producing states in New England.

"This is a scare we've lived with for a long time," Darre said.

He said state and industry officials were first put on alert in the early 1980s when a strain of avian influenza was discovered in eastern Pennsylvania.

That strain resulted in the destruction of 17 million birds in addition to the hundreds of thousands that died from the disease, according to Pennsylvania veterinarian and poultry consultant Dr. Dave Kradle.

It resulted in a statewide surveillance program in Pennsylvania that remains in place today, Kradle said.

That strain also was considered a low-risk pathogen but quickly mutated to something more serious. That is the concern with the influenza suspected in Connecticut, Kradle said.

"Although the symptoms in flocks are not nearly as severe, you can really miss it if you're not looking for it," Kradle said.

As a result of the Pennsylvania outbreak, Connecticut tightened its biosecurity in the industry, Darre said. But wild birds such as ducks and geese can be carriers, and because Connecticut is on a major migratory flight path the potential exists for the disease to be deposited here, he said.