An outbreak of swine flu in Mexico may have killed up to 81 people so far this month while more than 1,300 were suspected to be infected, Health Minister Jose Angel Cordova said late Saturday.

Since April 13, "there have been 81 registered deaths which are probably linked to the virus, of which only 20 cases have virological checks," Cordova told a news conference after meeting with health officials from across the country.

He said a total of 13 new cases were reported in the past 24 hours, bringing the total number of patients with flu symptoms under investigation to 1,324.

According to the World Health Organization, the virus from 12 of the Mexican patients is genetically the same as a new strain of swine flu, designated H1N1, a mixture of swine, human and avian flu viruses.

Cordova also announced to extend the school closures in Mexico City, neighboring Mexico state and the northern state of San Luis Potosi with swine flu outbreaks, for more than 10 days till May 6.

On Friday, the Mexican Army distributed 6 million face masks to citizens in Mexico City. Information stations were also established in the capital to provide precautionary measures to citizens.

Mexican authorities have cancelled hundreds of public events in the capital to prevent the further infections. The Diving world series 2009 and several football matches were forced to be held behind close doors.

In the US, health authorities have confirmed 11 cases of swine flu in Kansas, Texas and California. Eight suspected patients were also found in New York City.

WHO declared the outbreak a "public health emergency of international concern" on Saturday.

(Xinhua News Agency April 26, 2009)