A school in L Section, Umlazi had to be shut down when around 70 pupils and teachers were admitted to hospital after inhaling an unknown chemical.
Rescue Care spokesperson Garrith Jamieson said they received numerous calls after 09:30 on Monday.
"We dispatched multiple units to assist. On arrival, we were met with total chaos."
Jamieson said a chemical in the air at the Vukuzakhe High School grounds was the source of the problem.
"It is believed that boys were kicking around some kind of ball and the ball cut open and a chemical was emitted from it."
He said one patient had to be airlifted to the eThekwini heart hospital after sustaining critical injuries and that between 60 and 70 pupils and staff were rushed to other hospitals.
"At this stage, the chemical substance is unknown but police are in attendance together with the bomb squad, Durban Search and Rescue and Metro Search and Rescue who will investigate further."