Avian influenza has been confirmed at a large chicken farm near Regina, officials with the Canadian Food Inspection Agency said Thursday.

The H7N3 strain of the virus found at Pedigree Poultry at Regina Beach is fatal to birds, but is not dangerous to humans, the agency said. All 50,000 birds at the farm will be destroyed with carbon dioxide gas over the next few days.

Saskatchewan farmers produced about 23 million chickens in 2005, according to the provincial Agriculture Department.

"We could consider the entire premise to be infected," CFIA veterinary specialist Sandra Stephens said.

Speaking to reporters in Regina, Stephens said eggs produced at the farm have been hatched at another facility, but added that the virus couldn't be carried by chicks born from those eggs.

Stephens said the H7N3 subtype is not normally associated with serious human illness. When asked whether any of the people around the farm have been tested or were sick, Stephens said that was a question for health officials.

The U.S. Department of Agriculture responded to the news by closing the border.

"USDA is barring imports of all live birds, including chickens, turkeys and others, along with unprocessed avian products from the entire province of Saskatchewan," the USDA's chief veterinary officer, John Clifford, said in a news release.

Clifford also said the U.S. hasn't imported poultry products from Saskatchewan since 2005. That wasn't as a result of a ban.

Earlier in the day, the road to the quarantined farm was blocked off about a kilometre away, and an official in a car was making sure nobody tried to get through. The official told a CBC reporter anyone coming out would be disinfected.

Officials with the local rural municipality were issuing a warning to the public.

"I would advise people to just stay away from the area because if there is a disease issue, we don't need to have any of this spread about either in our area, or any other area," said Jim Hipkins, reeve for the rural municipality of Lumsden.

Vehicles leaving the farm Wednesday were seen having their tires washed. People walking in the area were also seen having their footwear sprayed down.

Stephens said equipment and tools at the facility will be cleaned and disinfected in the days ahead. A three-kilometre control zone has been established around the farm, but the facility is the only one in the zone with poultry, she said.

However, there is a Hutterite colony with a 65,000-bird chicken operation about eight kilometres away from the Pedigree Poultry site.

Virus commonly carried by migrating birds

Nobody knows how the infection spread to the Regina Beach-area farm, but the virus is commonly carried by migrating waterfowl, Stephens said.

Regina Beach is about 55 kilometres northwest of Regina.

Health authorities are concerned about avian flu because of the way the virus can jump to other species, including humans. Some believe avian flu could someday cause a worldwide pandemic.

Around the world, 200 people have died of a different strain of the avian flu - H5N1 - since 2003, according to the World Health Organization.

The H7N3 strain that was found at the Saskatchewan farm has been known in rare cases to transfer to humans, but it's not considered a significant threat, according to Shauna Hudson, a community health specialist with the Saskatchewan Health Department.

An outbreak of H7N3 avian flu on a poultry operation in British Columbia in 2004 saw two people infected, but they suffered only mild flu-like symptoms.

However, the poultry industry took a major blow when the disease forced the destruction of more than 17 million birds.