Mexico laboratory tests have now confirmed 866 cases of the new strain of A/H1N1 flu, including 26 deaths, Health Minister Jose Angel Cordova Villalobos told media on Tuesday.

However, Cordova added that there are no testable samples for 77 people who died suffering symptoms consistent with H1N1 flu including breathing difficulties.

The World Health Organization said 1,124 people worldwide has infected with the H1N1 flu.

"Deaths which were reported as suspicious numbered 214. Of these 74 have been definitively ruled out by clinical studies," Cordova said. Of the remaining 140, "26 have been confirmed ... 37are pending ... and 77 people who died of what we will never be able to prove anything either way," he said.

Nearly 51 percent of total cases are in people under 20. However, most of the confirmed deaths were of people between 20 and 30 years old. Some 78 people in total are in hospital with the disease, he said. Earlier on Tuesday, Mexico City health chiefs said that 68 people are in hospital in the city.

The nation closed educational institutions last week, effectively sending home 33 million people. These institutions will reopen in stages, starting with higher education institutions on Wednesday. Nurseries and primary schools will be the last to reopen on Monday.

In Mexico City, anti-flu measures were even stricter including the closure of all places where people gather and the widespread use of face masks. The government recommended citizens stay home, wash their hands regularly and use face masks if they have to go out.