U.S. health officials expressed concern Friday that a swine flu virus that has infected eight people in the United States matches samples of a virus that has killed at least 68 people in Mexico.

U.S. health experts also are concerned because more than 1,000 people have fallen ill in Mexico City in a short period of time.

“This situation has been developing quickly,” said acting CDC director Richard Besser. “This is something we are worried about.”

New York health officials announced Friday they are testing about 75 students at a Queens school for swine flu after the students exhibited flu-like symptoms this week.

A team of state health department doctors and staff went to the St. Francis Preparatory School in Queens on Thursday after the students reported cough, fever, sore throat, aches and pains.

There have been no confirmed cases of swine flu there. The tests results are expected as early as Saturday.

Of the 14 Mexican samples tested by the Centers for Disease Control and Prevention, seven were identical to the swine flu virus found in Texas and Southern California, Besser said at a news conference.

An eighth U.S. case was reported Friday. All of the eight U.S. patients have recovered, Besser said. Video Watch for more on the U.S. cases »

As a precaution to avoid further contamination, schools and universities in Mexico City and the state of Mexico were closed Friday, said the national health secretary, Jose Angel Cordova Villalobos. He said the schools may remain closed for a while.

Sixty-eight people have died in Mexico City, Cordova said at a news conference. More than 1,000 other people have gotten sick, he said.

Mexican President Felipe Calderon canceled a trip Friday to northern Mexico so he could remain in Mexico City to monitor the situation, the state-run Notimex news agency reported. Calderon met with his Cabinet on Thursday night to discuss the outbreak.

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