On 9 May 1992 an underground explosion destroyed the Westray coal mine located in Plymouth, Nova Scotia, Canada. Twenty-six miners were killed. This paper attempts to resolve the multiple layers of accident causation by systematic application of a loss causation model. Immediate and basic causes having their origin in lack of management control are identified. The analysis helps to identify the lessons to be learned from this disaster, the two most important of which are the need for a rigorous loss management system and an appropriate attitude toward industrial safety.