MEXICO CITY — Mexico canceled school nationwide Monday and warned the death toll from a swine flu epidemic believed to have killed 149 people would keep rising before it can be contained.

Health Secretary Jose Angel Cordova said 20 of the deaths have been confirmed to be from swine flu and the government was awaiting results on the other deaths.

"We are the most critical moment of the epidemic. The number of cases will keep rising so we have to reinforce preventative measures," Cordova said at a news conference that was briefly shaken by an earthquake centered in southern Mexico.

Cordova said 1,995 people have been hospitalized with serious cases of pneumonia since the first case of swine flu was reported on April 13. The government does not yet know how many were swine flu.

Of those hospitalized, 1,070 have been released.

Cordova said school at all levels nationwide were suspended until May 6, extending an order already in place in Mexico City and five of the country's 32 states.

At least two weeks after the first swine flu case, the Mexican government has yet to say where and how the epidemic began or give details on the victims.

Cordova said the health department lacked the staff to visit the homes of all those suspected to have died from the disease. But he assured that the country had enough medicine to treat the ill.

Labor Secretary Javier Lozano Alarcon said employers should isolate anyone showing up for work with fever, cough, sore throat or other signs of the flu.

The Mexico City government is considering a complete shutdown if the death toll keeps rising, including all public transport. Mayor Marcelo Ebrard said surgical masks were being distributed at subway and bus stops across the city.

The disease has hit hardest in the capital, but life was disrupted from Tijuana to Acapulco, a lucrative Pacific resort town where night clubs and bars were ordered closed until further notice. Acapulco Mayor Manuel Anorve Banos said he was worried about tourists from Mexico City spreading the disease.

Some city dwellers headed to the beach, taking advantage of the closed schools. But those who live day-to-day worried about making ends meet if the city completely shuts down.

"We're going to have to stop working," said Raul Alvarez Torres, who relies on the subway to get from his gritty suburb to his shoe shining stand in an upscale Mexico city neighborhood each day. "If people have no transport, getting around is impossible."

For the first time in 300 years, the cathedral in Mexico City's main plaza has pulled an icon of the Lord of Health from storage, and worshippers placed it on the principal altar.