Around 5:30 pm, a chlorine leak occurs on a hot water spray system used to evaporate chlorine from an aluminum smelter. At 5:43 pm, a person who smells chlorine outside the facility alerts the rescue workers. The latter put in place a perimeter of safety and cut the road traffic. By radio, the public is informed, at 19:46, of the need to confine themselves to their home. Firefighters locate the chlorine leak and stop the hot water spraying system. The leak is stopped, at 19:35, by raising the socket and the valve stem. Concentrations of chlorine at the site border are in the range of 6 to 20 ppm. Intoxicated, 4 employees and 4 policemen are hospitalized for 24 hours in observation.

Aluminum melting is carried out in 3 foundry furnaces at temperatures of 800 to 1000 ° C. One of the stoves has a capacity of 20 t / charge, the other 6 t / charge. Chlorine is used to remove magnesium from the melt. The site has two 500-liter chlorine cylinders located in a special, partially open room. One cylinder was connected to one chlorination unit while the other was kept in reserve. The closing valve on the cylinder is provided with an extension rod which can close the valve from the outside. This rod can be activated only in emergency situations as instructed by the chlorine supplier.

The cause of the accident is the unscrewing of the socket and the valve stem. These have been unscrewed by force, avoiding the locking provided by a locking screw. After that, the socket and the valve stem would have been ejected or removed, causing chlorine to leak. The operator reports that the workers present at the time of the flight are foreigners and that, consequently, language problems may be involved in the accident.

After this accident, the extension rod is equipped with a one-sided ratchet wrench ensuring that, if actuated from the outside, only the closing of the valve is permitted.