MANHATTAN, Kan., (KSNT) – A mysterious outbreak that’s plagued Manhattan High School for two weeks has now expanded to the elementary and middle schools in the district, the superintendent said Friday. A district wide plan to clean all schools and buses in the district is underway.

State and local health officials have been unable to determine the cause of the sickness, which has sent about 150 high school students home from school with stomach issues, including nausea, vomiting and diarrhea. Superintendent Marvin Wade calls the issue unusual and says “an unusually large number of students” are impacted.

On Friday, Wade said elementary and middle school students started reporting similar symptoms. The only difference is some younger students were reporting a fever, which has not been a symptom of high school students.

The principal of the high school Friday issued a desperate plea for sick students to provide stool samples to help health leaders determine what was causing the illness.