At 6:55 p.m., in a hazardous waste processing plant, 3 explosions occurred in the copper kiln used to prepare metal packaging to hold residues of a liquid mixture of methyl iodide and chloropicrin. A pink gas, probably containing iodinated compounds, escaped through the damaged door. Technicians reduced the amount of waste being introduced into the rotary kiln and increased the speed of its exhaust fan to detect emissions travelling from the copper kiln to the central post-combustion facilities. At 7:05 p.m., a water sprinkler system was set up to reduce the emissions. At about 7:10 p.m., the opening in the door was sealed off with biological refractory fibre.

The incident produced a widely visible plume of smoke. The dispersion modelling of toxic emissions carried out by the facility operator determined a 56 m perimeter of irreversible effects threshold within the boundaries of the site. The copper kiln was out of service for 8 days.

The cause of the incident is said to have been the incomplete emptying of cylinders, causing a pressure rise and explosion under the effect of heat. Most of the cylinders had been emptied by nitrogen flushing. However, as some were clogged, they were drained after having their valves and fittings sawn off. The dip tube of some of these cylinders was probably blocked and did not allow the residual liquid to drain off.

The procedure for preparing the cylinders was modified to ensure systematic disassembly of the dip tubes by drilling of the brass head.