Eleven students and one adult have been discharged from Lehigh Valley Hospital after falling ill during Mass Wednesday morning at Assumption BVM Church in the Colesville section of Upper Saucon Township, according to a WFMZ report.

The students were fifth-graders at St. Michael the Archangel Middle School, which enrolls pupils from throughout Lehigh County.

It's still not known exactly what made them ill, although high heat and humidity could be to blame.

Officials originally feared a gas leak may have caused the students and adult to feel dizzy and nauseous after going from the school to the church. No unusual levels of natural gas were detected.

Five students fainted. Everyone taken to the hospital as a precaution was released later in the day.

The school was evacuated as emergency crews checked for a gas leak or other problems.