Mexico has activated a national emergency plan to contain a bird flu epidemic that has affected nearly 1.7 million poultry, the Agriculture Ministry said Monday.

The plan was set in motion last week after authorities had confirmed the existence of the H7N3 virus in the towns of Tepatitlan and Acatic in the western state of Jalisco, the ministry said.

Although the outbreak is now concentrated in the two towns, the plan "will be activated throughout the country to prevent the spread of the disease," it added.

Under the plan, tight controls are placed on the transportation of poultry, poultry products and other animals, and birds infected or at risk of infection will be destroyed.

More than half of the 1.7 million infected fowl have died or been destroyed, local media reported.