The cause of sickness of 30 students from a school in Springfield, Minn., who were treated for suspected carbon monoxide poisoning Thursday remains unknown after a second investigation Friday morning. There was no evidence found of carbon monoxide, natural gas or organic compounds or chemicals in the school, CenterPoint Energy spokeswoman Becca Virden said.
The school was evacuated and the ill students were treated at a Mayo Clinic facility in the town an hour west of Mankato. One student was still being evaluated as of Thursday evening, and the others were treated and released.
The school is closed Friday as the inquiry continues.
CenterPoint Energy officials helped investigate, though the utility doesn't manage gas in public buildings. Fire department personnel, along with an environmental company contracted by the district, also investigated.