Frederick County schools officials are trying to learn why so many students at Brunswick Elementary have gastrointestinal ailments.

Principal Gerald DeGrange sent a letter last week to parents saying many students have been missing classes.

But county schools health specialist Christa Williams says officials don't know what's causing the illness. She also says its not known exactly how many students have been or are sick.

A health specialist for Frederick County Public Schools says all sick children at Brunswick Elementary need to provide stool samples. The Frederick County Health Department will test the samples.