“Our initial finding shows some kind of spray was used by some of the students to freshen up the classrooms,” provincial police spokesman Col. Abdul Rauf Ahmadi told NBC News. “Our investigation is ongoing to determine if it was an act of sabotage or poor quality spray.”

Forty of the 94 sickened girls from a minority Shiite neighborhood were admitted to hospital after feeling ill at school, Herat’s police chief Gen. Majid Rozi told NBC News. All were were feeling better and in good health by Monday afternoon, he added.

Fundamentalist Sunni Muslim Taliban militants have a history of targeting both girls’ schools and the Shiite Muslim minority in Afghanistan. However, the group did not immediately claim responsibility for Monday’s incident.