A natural gas leak forced Byron-Bergen administrators to dismiss students around 9:30 a.m. Thursday.
The district said both the junior and senior high school and the elementary school were impacted.
Students were evacuated from the building after a building and grounds employee at the school smelled what they believed to be natural gas.
Students were kept outside the building while administrators and emergency crews investigated.
A short while later, the school day was ended and students were sent home. After school activities were also cancelled.
The district says it will notify students by phone on whether or not there will be school Friday.