Four girls were slightly injured during a police explosives demonstration at their school as part of a career day in Batho, in Bloemfontein, today.
Police spokesperson Captain Rulene Kuhn said a container exploded at the Academy of Learning in Batho at 9.30am during the demonstration.
Kuhn said the area had been cordoned off, but somehow explosives in a container standing to one side ignited.
Four primary school pupils were treated on the scene and taken to the Pelonomi Hospital.
The police, ambulance services and fire brigade took part in the career day exhibition.