Within a chemical plant during a thunderstorm, plant personnel started up a nitration process following a power outage. A nearby lightning strike and a fireball could be observed; flames tens of cm high were visible on the lid of the nitration device. The fire was extinguished in 10 sec by drainage of the nitration line (automatic blow-down). The lightning did not fall onto the adjacent lightning rod but instead on the roof of the reactor building, thereby deteriorating the heat insulation and cables located adjacent to the device. Inspections indicated the compliance of the electrical installation. The incident was caused by an indirect effect of the lightning. A lightning risk evaluation was commissioned. The exact date of the accident remains unknown.