A fire broke out at night in a 50-m² storage building located inside a varnish plant whose installations were shut down. This space, which was physically removed from the other onsite installations, housed 5 tonnes of nitrocellulose in combinations of 20-kg cardboard boxes / sealed bags or 200-litre barrels / sealed bags. The fire destroyed the stock and damaged the building. The heat flow was responsible for destroying a medium-voltage electrical line in alignment with the storage area and damaged the separating fence. The extinction water flowed into a creek, yet no traces of soot could be detected. Given the inactive state of the storage room along with the evidence of lightning having struck the electrical line, the hypothesis of a lightning bolt was preferred. One individual was slightly hurt. The site operator was requested afterwards to establish a report. The operating loss related to the disappearance of the nitrocellulose inventory was valued at 15,000 euros.