About 9:30 p.m., January 1, 1968, Pennsylvania Westbound freight train PR-11A, consisting of 98 cars and five-unit diesel-electric locomotive, was passing Dunreith, Indiana, at 42 miles per hour when the trailing wheels of the 88th car, an empty tank car, AESX 850, derailed at a broken rail near the eastern edge of the town. At the same time, eastbound freight train SW-6 consisting of a five-unit diesel-electric locomotive and 106 cars, was moving eastward at 32 miles per hour on the adjacent track. The derailed car in train PR-11A continued westward until it became disengaged from its trailing truck when it struck the crossing board at a grade crossing about 723 feet west of the point of original derailment. One or more cars collided with cars of hazardous materials moving in the opposite direction in SW-6's train, causing a general derailment and puncturing several tank cars of flammable materials. A large-scale fire ensued, followed by a violent explosion of a tank car of ethylene oxide forty-five minutes later. Immediately after the derailment and outbreak of fire the population of Dunreith was evacuated without injury. A cannery and several residences and businesses were destroyed. Three firemen and two policemen were slightly injured in the fire and explosion.