STOCKTON (CBS13) – The Stockton Unified School District is looking into why several students at Hong Kingston Elementary School experienced light headedness and passed out Wednesday afternoon, just before school dismissal time.

The district placed the school on lockdown so first responders could treat affected students. Four students were transported to area hospitals for tests. None of those students were admitted to the hospital.

The Stockton Unified School District already tested the cafeteria, kitchen, campus food, and air and are waiting for the results. Those areas were also cleaned thoroughly.

Hong Kingston Elementary is open Thursday for classes.