The pigs are thought to have been infected by a Canadian farm worker who recently visited Mexico and got sick after returning to Canada.

The estimated 200 sickened pigs are recovering, officials said.

The World Health Organisation (WHO) has insisted there is no evidence that pigs are passing the virus to humans.

Pork trade

The UN Food and Agriculture and WHO issued a statement saying there is no justification for anti-pork trade measures as a result of the swine flu epidemic.

The statement was given after major American pork importers like Russia and China banned pork products from certain US states.

Ukraine, Indonesia and the Philippines have banned certain pork products from their country.

Canadian officials said these measures were unwarranted.

Egyptian authorities have begun slaughtering 300,000 pigs, although the WHO has criticised the move, stressing no evidence of pigs transmitting the swine flu to humans exists.

Dr. Brian Evans, executive vice president with the Canadian Food Inspection Agency, said pigs were likely infected in the same manner as humans worldwide.

"Whatever virus these pigs were exposed to is behaving in that exact manner as those we regularly see circulating in North America and in swine herds in virtually every nation around the world,'' Evans said.

The new virus has so far shown no signs of mutation when passing from human to
pig, Evans added.