CHICAGO (AP) — It wasn’t the food.  County health officials say there appears to be no connection between food served at Chicago’s Shedd Aquarium and flu-like symptoms suffered by more than 100 students from Andrew High School.

They held their prom at the aquarium on April 27.

Kimberley Conrad-Junius, a spokeswoman at the health department, tells The Daily Southtown that several students felt ill before the big event. Two students tested positive for Norovirus.

About 400 people attended the prom.

Norovirus is contagious and causes inflammation of the stomach and intestines. Symptoms include vomiting, diarrhea and fever.

The Cook County Health Department says they are still investigating the incident. The Health Department is working with partners at the Chicago Department of Public Health and the State to determine a cause for the illnesses.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)