HOUSTON -- For the third time since the start of the school year, several teachers fell sick at a northeast Houston school and were taken by ambulances to the hospital, KPRC Local 2 reported Wednesday.

A total of eight teachers left their classroom at Francis Scott Key Middle School, 4000 Kelley, complaining of shortness of breath, throat and eye irritation.

"All symptoms that scientific testing at this point is not showing a cause for these illnesses," said HISD spokesman Terry Abbott.

But the district will try to calm staff, student and parents fears with more precise testing from an industrial hygienist. A pulmonary occupational therapist will also review teacher symptoms to try and come up with answers.