The incident occurred when workers were weighing a barrel of 4-hydroxybenzohydrazide. There was a short circuiting in the weighing scale which led to an explosion.

Proximate causes:
• Defective equipment

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Survival Technologies