Carnegie Mellon University says 15 students have diarrhea, nausea and vomiting and 13 of those cases have been directly linked to a cafe on campus.

Thirteen of the students who are ill ate soup or sandwiches from La Prima Expresso on the Pittsburgh school’s campus on Monday or Tuesday. The owner of the business hasn’t commented, but school officials say certain menu items have been removed from the cafe as a precaution.

The school’s University Health Services is working with the Allegheny County Health Department to determine what’s causing the illnesses.

The school plans to post student alerts as more information develops.