Although it hasn’t been completely ruled out it seems doubtful carbon monoxide caused students at St. Joseph’s High School to become ill on Monday.

Donald Lloyd, superintendent of administrative services for Greater Saskatoon Catholic Schools, says what happened to the students remains a mystery.

“We have not found anything to date that would indicate carbon monoxide or any other substance being in the school’s air envelope”, says Lloyd.

Fifteen students in two separate classes reported having headaches and feeling nauseous. They were taken to hospital for precautionary reasons. The majority were back in school on Tuesday.

Lloyd says everything at the school is functioning normally and there have not been any air quality problems in the past. Temporary CO detectors have been set up in the school.

Lloyd says building codes do not require CO detectors to be installed in schools but the division will be looking into the possibility of making them mandatory.