A hydrogen explosion at the Elkem Silicones site in Saint-Fons, near Lyon, injured four employees, three critically. The explosion occurred in an experimental workshop, igniting a fire that required 100 firefighters to control. Authorities activated an emergency response plan, ordering over 100,000 residents to shelter. The A7 motorway was closed, but reopened later. The site has a history of incidents and is classified as a high-threshold Seveso site, indicating strict regulatory oversight due to hazardous materials.