Specialists are on scene at the Grand Valley and District Community Centre today assessing what could have caused a carbon monoxide leak Sunday.
The facility is being examined in respect to the fuel burning appliances, and also the zamboni.
Dufferin County Emergency Management Coordinator Steve Murphy says EMS crews took 13 people to hospital.
An off duty paramedic playing hockey was the one who sounded the alarm after noticing the similar symptoms being experienced by people in the arena at the time.
He believed the symptoms were consistent with carbon monoxide exposure.
The community centre will remain closed today for the inspection and could reopen Tuesday.