The school was rapidly evacuated and all the pupils were assembled at the assembly point outside the school. Very soon smoke divers noticed that the smoke was coming from a smoke grenade, which had been defused in one of the pupil toilets. A thin white smoke including zinc chloride caused stinging and irritation from the respiratory tract.
Zinc chloride is an irritant gas which can cause severe pulmonary damage including pulmonary oedema.
Approximately ten pupils presented symptoms from the respiratory tract and they were primarily taken care of by the ambulance personnel until the medical team arrived. To transport those with minor injuries, a large bus was ordered from the adjacent air force base. It took two hours before the last pupil needing hospital care had left the accident site. In all 24 persons were transported by ambulance to the University Hospital and approximately 30 by bus. Apart from the task of localizing and identifying the smoke grenade, the police were responsible for cordoning off the area.