Unidentified illness keeps 242 students out of U.S

    HOUSTON, May 14 (Xinhua) -- One-third of the students at an elementary school in Houston, the U.S. state of Texas missed school on Thursday because of a mysterious illness, leaving education and city officials scrambling to identify the cause.

    Officials suspect a virus might be the cause of the fevers, headaches and stomachaches that sickened 242 children at Travis Elementary School, according to the local newspaper Houston Chronicle.

    That's a sharp increase from the 86 students who fell sick and stayed home on Wednesday.

    The children should stay home until they are fever-free for at least 24 hours, officials said.

    Some families have reported that their children have tested positive for Influenza A, a common form of the flu, according to media reports.

    Health officials said they have not ruled out environmental factors or even the new A/H1N1 flu. Food poisoning also might be the cause.

    An investigation is underway, officials said.