SAND SPRINGS, Oklahoma - Sand Springs Public Schools says they evacuated all students from Clyde Boyd Middle School Monday afternoon.

According to school officials, the evacuation is due to a heater malfunction and the possible presence of carbon monoxide (CO). SSPS says students are not permitted to go back into the building to collect their personal belongings until the Fire Department has given the all clear.

Clyde Boyd Middle School will remain closed on Tuesday the district says they will notify students and parents when they are allowed to re-enter the building. 

During the evacuation, all children were relocated to a large gym. All students have since been released to their parents. The evacuation did not include the 6th-grade center.

Sand Springs Fire confirmed that some students began to feel the effects of the gas. Firefighters said the readings were 100 ppm and 35 is enough to prompt evacuation. The building has no carbon monoxide detectors because they weren't required for older buildings, so the only indication was students who were ill.