OKLAHOMA CITY - Classes are canceled at Lee Elementary School Tuesday after several teachers and staff fell ill from carbon monoxide poisoning.

The school was evacuated around 2:30 p.m. Monday after several students and staff complained of nausea, dizziness and stinging eyes.

ONG and OKC Fire Department responded and tested the building for gases including carbon monoxide and found that carbon monoxide was confirmed in one classroom. The HVAC unit was found to be the source of the problem.

OKCPS will be removing that unit on Tuesday to replace it with a new one. While the building is now considered safe, the district has decided to err on the side of caution by closing the school on Tuesday.

The OKCPS Operations Team will conduct additional scans Tuesday to reassess and confirm the safety of the building.

Five students were treated at the scene, one of them transported by EMSA. Two students were taken to the hospital by their parents. Five Lee Elementary staff members were treated, three of them transported to the hospital by EMSA.