The AGO says in a statement that paramedics were called after the children became ill at the "Frida & Diego" exhibition space at the Toronto facility.
Paramedics say five children — all between the age of 11 and 12 — complained of flu-like symptoms and were treated and taken to the Hospital for Sick Children.
Fire officials say a hazmat team found nothing out of the ordinary after testing for carbon monoxide, carbon dioxide and oxygen content, so the source of the illness remains a mystery.
After receiving clearance from the fire department, the "Frida & Diego" exhibition space was re-opened.
Toronto police say they are continuing their investigation and focusing on other potential causes outside of the gallery.
(The Canadian Press, CFRB)