Four Injured In UPS Explosion File Lawsuit - LEX18 Four people injured in an explosion at UPS Freight in Lexington have filed suit against the company who shipped the acetylene tanks that are being blamed for the incident. The explosion happened in May of last year when a torch ignited acetylene gas that was apparently leaking from a tank on the back of a UPS truck. Witnesses in the building heard a large blast and saw debris flying from the building. Part of the roof was damaged. Forty-five cylinders were eventually counted on board the truck and were being shipped by a company called Praxair.