NEW YORK - Several hundred students have fallen ill at the New York school hit by a swine flu outbreak, city officials said today as the number of confirmed cases in the United States rose to 64, with at least seven people hospitalized.

A U.S. health official said deaths were likely.

"I fully expect we will see deaths from this infection," as swine flu cases are investigated, said Richard Besser, acting director of the federal Centers for Disease Control and Prevention.

New York has the largest number of swine flu cases, with a heavy concentration at a Catholic school in Queens where students recently went on a spring break trip to Mexico.

There were indications that the outbreak may have spread beyond the school, with two people having to be hospitalized and officials closing a school for autistic children down the road. Those cases have not been confirmed.

"It is here and it is spreading," New York City Health Commissioner Thomas Frieden said. "We do not know whether it will continue to spread."