School buses were rerouted and staff evacuated Tuesday morning following reports of a carbon monoxide leak at Floradale Public School in Woolwich.
No students entered the building but two staff members experienced some symptoms of carbon monoxide poisoning and were treated by paramedics.
One staff member was a teacher who had arrived at the school early in the morning, and the other was the morning custodian.
"When our custodian arrived he noticed there was a bit of an odd burning smell in the building," said Waterloo Region District School Board superintendent Elaine Ranney.
Emergency response services were called, and they believe the carbon monoxide leak was caused by a heater on the roof of the school that was damaged by high winds, she said.
"The staff acted appropriately and followed all school and board procedures," said Ranney. "I'm happy to report that all staff and students are safe."
Floradale Public School is expected to be open Wednesday for regular classes.