The 27th of March 2003, an explosion caused the death of four employees in a Nitrochimie pyrotechnic plant, at Billy Berclau, in the north of France. Following the accident, the ministry of Ecology and Sustainable Development appointed INERIS to perform an investigation. According to the terms of reference, the investigation would cover technical (origins of the explosion, extent of damages) as well as organisational issues, as defined by SEVESO II safety management system requirements. This paper has a threefold purpose. It intends first to illustrate with an empirical case the current trend in safety auditing and accident investigation, targeting organisational factors, alongside human factors. There are not so many published cases of accidents analysed with an organisational perspective. Secondly, it shows that it is possible to investigate organisational dimensions (through articulation of safety engineering, safety management and human and social sciences) within reasonable time frames and a reasonable amount of resources. By focusing on key actors and asking appropriate questions related to key dimensions, investigating organisational accidents might not necessarily imply spending much more resources than other steps such as damage assessment, chronological construction or identification of technical scenarios, although there are also some prerequisite conditions needed to achieve this. Finally this paper should be seen as a technical communication beyond the pyrotechnic industry