At 11:35 am., e.d.t., on October 7, 1983, a Mack 3-axle tractor, Model No. R685ST, which was pulling an MC306 (AL) cargo truck semitrailer loaded with 8,600 gallons of gasoline, was traveling in the right lane of westbound I-76 (Schuylkill Expressway) in Philadelphia, Pennsylvania, when it veered leftward, crossed the left lane, and collided with a concrete New Jersey-type median barrier. The combination vehicle overturned on the barrier, and gasoline, which spilled from the tank, was ignited. Three eastbound vehicles, which were caught in the area of the fuel spill, subsequently burned. Two persons were fatally injured, and one person was seriously injured.
After firefighters arrived onscene and extinguished the fire, smoldering fire caused the reignition and explosion of excess fuel trapped beneath the westbound access ramps. Two firefighters and a news media person were injured during the subsequent explosion.