* More cases expected; not clear when outbreak will end
* Schools to be closed across country until May 6
* Virus most lethal if not treated in 48 hours (Adds quotes, details, byline)
By Mica Rosenberg
MEXICO CITY, April 27 (Reuters) - An outbreak of swine flu has killed up to 149 people in Mexico and the number of cases is likely to rise, Health Minister Jose Angel Cordova said on Monday.
The government ordered schools throughout the country to close until May 6 to try to control the spread of the virus, adding that suspected swine flu deaths had been reported in 10 of the country's 31 states.
"We need to recognize that we are in the most critical moment of the epidemic and that the number of cases will continue to increase," Cordova told a news conference in Mexico City.
Most of the those who died were between 20 and 50 years of age, a worrying sign because a hallmark of past pandemics has been the high rate of fatalities among healthy young adults.
Governments around the world rushed to reduce the impact of a possible flu pandemic as the virus spread to the United States, Canada and Europe.
The new flu strain spreads quickly between humans but it has so far only killed people in Mexico, where there are 1,995 suspected cases. More than half of those suspected cases have been sent home with a clean bill of health.
Some 700 people are still hospitalized as the government rushes to confirm through laboratory tests if they are sick with swine flu.
Late detection or treatment could be responsible for the deaths since patients who receive medicine within 48 hours are more likely to recover, Cordova said.
Although it is not clear when the epidemic in Mexico will subside, a vaccine for the new strain could be developed within the next six months, he said. (Additional reporting by Miguel Angel Gutierrez; Editing by Eric Beech)