Mexican Health Minister Jose Angel Cordova said Monday that cases of influenza in early April in the Gulf Coast state of Veracruz didn't cause the government to raise an alarm because it had no immediate reason to suspect the emergence of a new strain of swine flu.

The new strain of flu is suspected in 149 deaths so far in Mexico in a major influenza outbreak that has taken on international dimensions, with the World Health Organization warning of the possibility of a global pandemic.

At a press conference, Cordova said most of the cases found in the Veracruz town of La Gloria, near Perote, were linked to the known strain H2N3, adding that people affected were given standard flu treatment and there were no fatalities.

Cordova defended health authorities' actions in the case of Veracruz and said neither Mexican nor international standards at the time would have called for it to be cause of an alert for a potential epidemic.

The first death from the new strain of swine flu virus was recorded on April 13 in the southern state of Oaxaca, samples of which were sent to the U.S. and Canada for further testing several days later.

Cordova said a sample was kept from a four-year-old boy in Perote. When more flu cases appeared elsewhere in the country, that sample was sent for testing along with other confirmed cases and was found to be the new strain, he said.

According to the U.S. Center for Infectious Disease Research and Policy at the University of Minnesota, the H2N3 virus is related to various strains of regular swine flu that has been known to infect pigs. Regular swine flu doesn't normally cause human deaths.

The new deadly strain - A/H1N1 - hasn't been discovered in pigs so far and is a mix of swine, avian and human influenza.

Residents in Perote complained to local authorities after about a third of the population came down with the flu, which they blamed on a local pig farm operated by Smithfield Foods Inc. (SFD), according to local media reports.

Smithfield said Sunday that it had found no evidence of swine influenza among the herds or employees at its Mexican operations. "Smithfield has no reason to believe that the virus is in any way connected to its operations in Mexico," the company said. Smithfield shares on Monday fell 12% to $9.04.

Swine flu symptoms in humans are similar to those of regular human influenza and include fever, lethargy, lack of appetite and coughing, according to the Centers for Disease Control and Prevention, or CDC.

-By Maja Wallengren and Anthony Harrup, Dow Jones Newswires; (5255) 5001 5725, maja.wallengren@dowjones.com

(Debbie Carlson in Chicago contributed to this report)