Around 11 pm, a fireworks show started in the Cébazat city park in the presence of some 1,000 spectators. Shortly after the first rockets were fired, between 5 and 10 projectiles were propelled horizontally and exploded adjacent to where the public had congregated in back of the barricades just tens of metres away, creating crowd panic and jostling. Nine spectators, including four children, were slightly injured; they were transferred to 2 hospital facilities in the Clermont area and released during the night to return home, only sustaining slight superficial burns and hearing discomfort.

The origin of these defective firings remains unknown. The extremely high humidity following rainfall over the previous days might offer one explanation; the humidity would have softened the cardboard mortars that are used to propel fireworks. According to other sources, the mortars had been fastened to a barrier that swung after the first firework was shot since a second barrier, which served to secure the entire batch, would have been shifted after its installation by the team of pyrotechnicians. A police investigation was ordered.