A day after dozens of Woodland Hill Elementary missed school or fell ill during classes, the sick toll rose to the hundreds on Thursday morning.
At least 200 students are absent today at the grade school in Greenwood, which is part of the Humble Independent School District.
School and district officials don't know why.
A letter sent home to parents asks that sick kids be kept home and taken to a doctor. At school, students are being asked to wash their hands thoroughly -- and bathrooms and doorknobs are getting extra cleaning. There's also a nightly overnight cleaning plan under way.
Health officials are investigating.
"Vomiting and diarrhea appear to be common symptoms," principal Debi Beard states in her letter to parents. "At this point, the cause of the illness is not known. No other campuses have reported unusual numbers of absences."
Beard also says the Harris County Health Department has been contacted "as a precaution."
"They have asked to speak to a small selection of parents to aid in their investigation and determine if any additional steps need to be taken for prevention," Beard states in her letter. "If your child exhibits any symptoms of a stomach ache or diarrhea, please keep your child home and seek advice from your physician."