Approximately 65 students were sickened from exposure to carbon monoxide at Jo Byrns High School in Cedar Hill Friday.
Robertson County Schools' spokesperson Jim Bellis told Nashville's News 2 the gas was caused by a power pump being used outside the school to pump water from underneath the building.
He said the pump was being used too close to an air intake vent, which caused the gas to get into the building.
The affected students are in grades six and seven.
They were moved to the school's gym where they were examined by emergency personnel.
All were given a clean bill of health and released to their parents.
Bellis said carbon monoxide levels never reached critical or dangerous levels. He said the exposure was similar to leaving a lawnmower running in garage
CO2 levels in the building have since returned to normal and the school will dismiss at 2:30 p.m. as scheduled.
441 Murfreesboro Road Nashville, TN 37210