Tokyo, Japan (CNN) -- At least 905 children have called in sick to schools in a suspected case of mass food poisoning in Japan's Shizuoka Prefecture, forcing the local government to cancel classes at 15 elementary schools to prevent the outbreak from spreading.
The children from Hamamatsu, a coastal city about 125 miles southwest of Tokyo, suffered vomiting and diarrhea, officials said Thursday, while 41 teachers and staff showed the same symptoms.
Authorities suspect the outbreak was caused by norovirus, a common source of foodborne illness.
The highly contagious virus was "detected in about half of the stool samples taken from sick pupils," said Horihiro Ishizaka, a Hamamatsu city public relations official.
The city's hygiene office is testing school lunches eaten by the students to confirm the cause of the outbreak, Ishizuka said.
Local news reports said the schools used an ingredient from one shared supplier.
The city has closed most of the affected schools and canceled classes at others through Friday in wake of the incident, which comes less than a month after 1,400 people across Japan fell ill after eating frozen foods that may have been tainted with pesticides.