Dozens of Centennial High School football players and their parents were sickened after eating at a banquet Monday night, according to the school’s principal. But the exact cause of the gastrointestinal illnesses has not been determined.

More than 100 people were affected, Channel 2 Action News reported.

Symptoms of the illness have included nausea, vomiting, diarrhea and abdominal cramps, Principal Kibbey Crumbley wrote in a letter to a parents of students at the Roswell school.

“Unfortunately, these symptoms can be associated with many different viruses and bacteria that could possibly be related to food-borne pathogens,” Crumbley said. “The best means of controlling these types of illnesses is to stay home when sick, wash hands frequently and clean surfaces thoroughly after contact with an infected or ill individual.”

Students with symptoms were urged to stay home and to see a healthcare provider, Crumbley said.

Both the Fulton County school system and the county’s health department are investigating the illness outbreak. One player’s mother told Channel 2 Action News her son had been diagnosed with salmonella, a type of food poisoning.

Foods contaminated with salmonella usually look and smell normal, according to the Centers for Disease Control and Prevention. Thorough cooking kills salmonella, but food can be contaminated by the hands of an infected food handler.

Last month, an outbreak of the highly contagious Norovirus sickened 89 Emory University students.