More than 30 schoolchildren have been admitted to hospital after they inhaled tear gas from canisters fired by anti-riot police during a morning drill in Osun State, local media reports.
It was taking place opposite Fakunle Comprehensive School, in Osogbo, but the fumes drifted over on to the campus.
The secondary school students were reportedly rushed to two different hospitals for urgent medical attention after losing consciousness.
The incident sparked panic as some parents quickly picked up their children after the school authorities were advised to close for the day.
Osun police spokesperson Yemisi Opalola apologised for the incident and said the officers would make the “necessary adjustments” to prevent a recurrence.