Emergency responders haven't yet determined a cause behind the mystery illness that struck St. Joseph Cathedral School on Wednesday.
Fire Chief Jason Turner noted at 7 a.m. Thursday that firefighters checked the school for appropriate oxygen, carbon monoxide and hydrogen sulfide levels. They also monitored the building's lower explosive limits, which is the lowest concentration of a gas or vapor in the air capable of producing a flash fire in the presence of a flame or heat source.
"Everything came back normal," Turner said.
Responders are still waiting for results - being performed by the Missouri Department of Natural Resources - of tests of possible contamination of the building's water source.
On Thursday, Principal Spencer Allen said it felt that life at the school was returning to normal.
"It seems like we're doing A-OK," he said, noting that the school nurse's office had only seen run-of-the-mill cases on Thursday.
He noted emergency personnel haven't been able to identify any connection to an environmental factor that might have triggered the students' symptoms, which included dizziness and rashes. Some students even collapsed.
He added the reported number of students - about a dozen - originally thought to have been affected may have been slightly exaggerated. He noted that school faculty, per the instructions of emergency workers, sent every student who had even minor complaints to be medically checked.
Allen also complimented emergency responders on the professionalism of their work. "They were fantastic," he noted.