What happened

During a main-replacement project, Columbia Gas crews abandoned a cast-iron gas main without relocating a pressure-regulator sensor line to the new main; when the old line was depressurised, the regulator sensed zero pressure and opened fully, feeding full main-line pressure into the low-pressure distribution network. The resulting series of structure fires and explosions across three towns damaged 131 structures, destroyed at least five homes, killed one person and injured 22 (including three firefighters). The NTSB cited 'weak engineering management' and a system built without adequate overpressure protection. This was an accidental infrastructure failure, not an attack.

When cited sources give different casualty, damage or spill figures for this event, they’re reported side by side above rather than merged into one number. See how confidence levels work.