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FORT LAUDERDALE (CBSMiami/AP) — Questions remain after a scary situation unfolded at a South Florida high school.

Classes resumed as normal at Cardinal Gibbions High School a day after 26 students and one adult staff member were hospitalized, including some who had seizures.

The school said in a statement Tuesday that Fort Lauderdale Fire Rescue and Broward County hazmat teams tested the school’s gymnasium, cafeteria and classrooms for more than 5,000 contaminants Monday but found nothing dangerous at the private Roman Catholic school.

Officials aren’t sure what caused some students to experience seizures, nosebleeds, shortness of breath or loss of consciousness. Everyone who was hospitalized Monday was treated and released the same day.

As a precaution, school officials say all air-conditioning coils in the gym cooling systems will be cleaned, and all filters will be changed.