The Piper PA-23-250 made an instrument approach to the airport. The pilot said he lowered the landing gear prior to touchdown, however, both propellers struck the runway. The pilot tried to make a go-around and the aircraft started to veer to the left. The pilot reduced power and the aircraft made contact with the dirt off the left side of the runway. The pilot and 2 passengers were not injured. Two passengers received minor injuries. Post-crash examination of the aircraft showed the landing gear and landing gear lights and warning horn worked properly, and that the landing gear was retracted when the aircraft touched down. No malfunction could be found. The pilot held a valid medical, however, his pilot certificate was commercial privileges ASEL and private privileges AMEL. He had received several checkrides from the FAA in multi-engine aircraft under 14 CFR 135 allowing him to operate as PIC in multi-engine aircraft without this being discovered by the FAA.