Thirty students from a school in Springfield, Minn. received treatment for suspected carbon monoxide poisoning on Thursday morning.
Mayo Clinic Health System spokesperson Micah Dorfner said the students were treated at the Mayo Clinic facility in the town an hour west of Mankato. One student was still being evaluated as of Thursday evening; the others were treated and released.
Dorfner said the students were treated for carbon monoxide poisoning but that the cause of the students' sickness is still under investigation.
The Associated Press reported that the school was evacuated shortly after 9:30 a.m., and that students and staff who weren't sickened were taken to the Springfield Community Center.
CenterPoint Energy employees helped authorities investigate the cause of the students' sickness, even though the company doesn't manage the gas in public buildings like schools, said CenterPoint spokesperson Rebecca Virden.
"We are not getting any carbon monoxide in the atmosphere now," Virden said Thursday afternoon. "We are working very closely with emergency responders and school officials, who have brought in an environmental testing agency, to try and work with our expert employees and determine what could [have] happened in that school that's not there now."
Virden said CenterPoint Energy employees have been asked to assist in the investigation again on Friday morning.
Springfield Public Schools Superintendent Keith Kottke said investigators will try to recreate conditions Friday to discover the cause of the sickness. He said school has been canceled at the K-12 facility on Friday.
The Associated Press contributed to this report.