The students of River East Collegiate had their banquet at the Winnipeg Convention Centre on Tuesday.
The parent of one grad who was vomiting and had diarrhea said people started getting ill on Thursday.
On Friday, a formal complaint was made to authorities.
The Winnipeg Regional Health Authority said it’s looking into the matter but hasn’t been made aware of any serious cases of illness.
Investigators are trying to determine the cause of the sickness, and whether it was a virus, food-related or caused by something else.
Officials from the school and the graduation committee did not respond to requests for comment.
(Winnipeg Free Press)