At least 29 students have died in a tragic stampede in Bangui, the capital of the Central African Republic, after an explosion sparked chaos during high-school final exams.

The students, who were among nearly 6,000 gathered at the Lycée Barthélémy Boganda to sit the national baccalaureate exam, were caught in a deadly crush on Wednesday after a loud blast nearby triggered panic. The explosion came from an electricity transformer, according to Abel Assaye, the director of Bangui’s community hospital.

“The noise of the explosion, combined with smoke,” led to widespread alarm, local radio station Ndeke Luka reported.

President Faustin-Archange Touadéra has declared a period of national mourning in response to the tragedy. He also ordered that the more than 280 people injured in the incident receive free medical care at hospitals.

The victims came from at least five Bangui schools. For students nationwide, the baccalaureate exams represent a significant turning point, but this year’s session has been tainted by tragedy and tragedy.

Political instability and insecurity have always been problems in the Central African Republic. Armed factions trying to topple President Touadéra’s government are still being fought by government troops supported by Russian mercenaries.