The outbreak of bird flu detected in the central Mexican state of Guanajuato is confined to 12 farms that have more than 1 million chickens, the Senasica national agricultural health service reported on Monday.
The agency said in a press release that 10 of the poultry farms are chicken-fattening operations and two produce eggs for human consumption.
Senasica, which is an agency under the control of the Agriculture Secretariat, said that all the affected farms are owned by the Bachoco company.
Last Friday, authorities decreed a health emergency due to an outbreak of avian flu on seven Bachoco farms in Guanajuato, where some 582,000 domestic fowl exposed to the virus could be slaughtered to eradicate it, officials said.
Health authorities confirmed the presence of "high-pathology" AH7N bird flu, "as was the case in the (Mexican) states of Jalisco and Aguascalientes" in 2012.
Last June, an outbreak of the virus led authorities and producers to sacrifice more than 22 million infected birds, causing a huge scarcity of eggs and chicken in stores and a concomitant escalation in prices.
When the new outbreak, was detected, Senasica established a quarantine "as established by international health protocols" around the affected farms and conducted preventive vaccinations at neighboring poultry operations to prevent the disease from spreading.
The agency also said that activities to "wash, clean and disinfect the facilities and equipment of each of the affected farms" were being carried out.
Senasica also noted that this virus is "exclusive to birds ... (and poses) no risk" to humans.
On the weekend, the Guanajuato governor said that more than 400,000 chickens will be slaughtered in an attempt to contain the virus.