St. Michael's School at 4121 Old Bethlehem Pike in Upper Saucon Township was evacuated after incident on Wednesday morning.
It all happened as students were inside the church on campus for a May Queen ceremony when four or five of the children began to feel a little bit nauseous, and then they passed out.
They were taken back over to the nurse's office in the school building, but by the time emergency crews arrived on the scene, all of the children had regained consciousness.
Several other children also felt ill. In all, ten kids and one teacher were taken to the hospital for treatment, but everyone is now OK.
"When we arrived on the scene, everyone had been removed from the church," according to Upper Saucon Valley Police Chief Robert Coyle, "and brought into the nurse's office."
What caused the sudden illness is still a mystery to officials. There was no natural gas in the building, no carbon dioxide, no odors were smelled by anyone inside the church at the time, and hazmat teams responded to the scene and found nothing.
There was a local gas company crew working just outside the church at the time, however, it is unclear if that could be related at all because no one smelled the odor of natural gas.
"We used probably 6 of our own meters that we carry between the 2 fire departments that were here," said Chief Charles Castetter of the Upper Saucon Valley Fire Department, "as well as Hazmat has specialized meters that look for things that our meters do not. Actually no readings whatsoever were found on any of the meters."
The kids were all from the same 5th grade class, so now officials are trying to figure out if they had something to eat or drink before they went over to the church.
The church's air conditioning system was on an working properly, so officials say heat exhaustion is unlikely.