State and Riley County health officials are working to determine why more than a dozen Manhattan High School students became ill this week.

Riley County health official Jennifer Green says the high school reported that the students had been sent home after reporting nausea and vomiting.

Green says at least 16 students were sent home between Monday and Thursday, and the school reported 19 students were either sent home Friday or had parents report they were ill.

The Topeka Capital-Journal reports the county health department did not find similar illnesses at other area schools.