During a school assembly for Armistice Day, one student at Outwood Academy in Ripon, England, began to feel ill. The boy was standing in the hallway and suddenly fainted.
"After that it was a bit of a domino effect," a student told BBC News. "Another three or four collapsed and then people started leaving the hall to get fresh air."
Four students fainted and others began feeling sick. As a precaution, the secondary school called the ambulance service, who treated 40 students on-site, according to a statement from the school. The most severe injury was a concussion caused by collapsing. Two students were brought to a local health care facility to be treated.
While none of the children were seriously harmed, the incident has teachers, students, and authorities scratching their heads. What could cause so many children to suddenly fall ill?
The fire department brought hazardous materials specialists to the scene, but no gas or chemicals were found. A firefighter told the BBC that he believed the room was hot and some children became overwhelmed and panicked.
Fire station manager Dave Winspear agreed: "We are of the view the children just fainted and there was a ripple effect throughout the school."