At least 107 people have been treated for gastrointestinal illness in an unidentified outbreak linked to a University of Notre Dame sports camp, the university reported Wednesday afternoon.

The number of those treated rose after the university first reported that youth sports camp participants had fallen ill just hours earlier.

“Some 80 youth sports camp participants at the University of Notre Dame were treated today on campus and at local hospitals for a gastrointestinal illness. All have been successfully treated for symptoms that are typical of the stomach flu and short-lived,” said the university in a statement issued around noon on Wednesday. “The cause of the illness is unknown, though it may be related to food or a virus and was not associated with any physical activity. The University is working with the St. Joseph County Health Department in an effort to determine the cause.”

The statement said those sickened were involved with football, hockey, women’s basketball, women’s lacrosse and women’s tennis camps.

Parents of campers were sent a letter on Wednesday mid-day to alert them of the outbreak. The university said, at the time that “more than 70 campers were sickened” and some were taken to the hospital.

The letter urged campers to take health precautions — like washing hands, avoid touching your mouth, and avoid sharing equipment like water bottles —  to help stop the spread of the outbreak.

Local new station ABC 57 posted the letter to parents online here.