Students and faculty were evacuated from the building on Tuesday and Thursday due to high carbon monoxide levels, and school was canceled for the afternoon on each occasion.
Doherty said that because both carbon monoxide incidents happened just after 11 a.m., firefighters and school officials were led to believe the leak could have been coming from the kitchen.
After Thursday's incident, staff found a piece of gas operated cooking equipment that had not been in use until late morning, which is when the detectors sounded. The equipment had not been used to prepare lunch on Wednesday, and there were no issues on that day.
"All other kitchen equipment has been tested and is functioning properly," said Doherty in his blog, posted on Thursday night. "We have taken the malfunctioning piece of kitchen equipment offline and will not be using it until it is replaced or repaired."