A series of explosions at an oil refinery reformer unit caused by a rupture to an 8 inch naphtha and hydrogen feed pipe. The large number of injuries was due to the close proximity of a construction crew working in the area. Two were declared dead at the scene and a further two later in hospital.The ensuing fires were quickly contained and extinguished, but caused offsite traffic within several blocks to be stopped.As a precautionary measure, a second reformer unit was shutdown pending the investigation. Fire officials cited higher than normal line pressures just before the blast. The reformer was being brought back on line after being shutdown for several weeks for repairs. Following the incident, it was expected that the plant would be returned to service within the month