An explosion took place at 11:19 am. in a building where double base propellant was produced in a explosive manufacturing company. The fifth propellant roll (16 kg) to be pressed exploded just after the technician pressed the start button. The press was a Hungarian machine manufactured in the 1940s designed for the pressing of the double base propellant, which was modernised at the 1980s. The piston assembly of the press (770 kg) was equipped with a hydraulic system to enable the lifting / lowering and keeping up the piston during filling of the cylinder.

The investigation could not identify with certainty the technical cause of the accident. However, the most likely course of events was judged to be the following:

Short after the start-up, the gasket of the lifting cylinder failed, which made the heavy piston loose. The suction pump that normally creates a vacuum could not because of the fast lowering of the piston. Thus, the air pressure in the pressing cylinder increased to several bars, causing a rise of the temperature. The propellant self-ignited then detonated due to confinement.

The technician in the press room, who had 20 years of experience at the double base propellant process, was killed on the spot. Three other technicians and the foreman ran out of the building and were not injured.

The cylinder and the surrounding iron cast heating jacket were partly fragmented. The major part of the fragments were stopped by the structural walls and earth wall surrounding the building. A few bigger fragments flew over the surrounding earth wall up to 200 meters. These fragments caused no damage to persons or material. The outer walls of the pressing room (light construction) and the roof were destroyed. The supporting structures were damaged. The floor of the building was slightly cracked. The downstairs windows were broken and fell outside the building. None of the windows of the other buildings were damaged. The explosion caused a fire in the pressing room. The fire spread to the vegetation on the earth wall. Part of the exterior roof of the pressing room was destroyed in the fire, which was quickly extinguished.

The operator modified the process : the press was changed to a horizontal press, no personnel will be allowed in the hazardous working areas. He developed the safety systems (risk analysis) and safety culture of the company.