While re-commissioning a steam pipeline (180°C and 22 bar) running through an underground tunnel, an explosion caused steam to be released. The workers undertaking repair operations at this phase were trapped in the tunnel by the steam and temperature flow. The workers in the technical tunnel (- 25 m) were killed on the spot (3 persons), as well as the ones at 10 m below ground level; eight out of nine other workers in other zones or at the upper level (at 3 m below ground level) sustained severe burns. The team was carrying out a delicate operation of increasing pressure on a 4.5 km section along with tests on the line. The operator presented the overall procedure as standard. Investigations were carried out to determine the causes of the accident.

In May 2013, the district heating company will appear before the Paris Criminal Court for homicide and involuntary injuries. The company is accused of failing to comply with its obligations in terms of ventilation and evacuation, as well as the means of protection made available to employees. According to the press, the investigation established that the release of steam was linked to the opening of a valve by an operator unaware of the danger of this manoeuvre.