An explosion and fire took place at the Shell Chemical Company Complex in Deer Park, Texas, on June 22, 1997, resulting in injuries, public sheltering, closure of transportation routes, and property damage both on and off site. EPA and OSHA undertook an investigation of this accident because of its severity, its effects on workers and the public, the desire to identify those root causes and contributing factors of the event that may have broad applicability to industry, and the potential to develop recommendations and lessons learned to prevent future accidents of this type. This investigation was conducted in conjunction with an investigation by OSHA to determine if violations of occupational safety and health laws had occurred.