On October 26, 1994, about 1446 central daylight time, a Bell 206B3 helicopter, N505KS, operated by EAC helicopters, was destroyed by impact and postcrash fire following an in-flight collision with transmission wires near Inver Grove Heights, Minnesota. The commercial pilot and three of the four passengers aboard received serious injuries; the remaining passenger received minor injuries. The 14 CFR Part 91 flight operated in visual meteorological conditions without flight plan. The purpose of the non-revenue flight was to give construction workers an aerial view of a highway project they had just completed on State Highway 55. The flight departed the South St. Paul Downtown Airport about 1420, and flew to a concrete mixing plant about 2 miles east-southeast of the accident site to pickup passengers for the flight. The flight then proceeded west along the nearby highway 55 at an altitude estimated by passengers as 75-100' agl. The return leg to the concrete plant was flown at a slightly higher altitude, 100-200' agl. A second group of passengers was loaded, and the flight flew west at a much lower altitude. Witnesses stated that the helicopter had to climb to cross the highway 103 bridge, and then descended again to fly along the highway. Witnesses reported the helicopter struck unmarked transmission wires situated perpendicular to the westerly flight path, and about 30' above ground level. The transmission wires were approximately 1,080 feet west of highway bridge 103. Highway 103 passes over the east/west highway 55 in a nearly perpendicular direction (north/south). The upper-most height of the highway 103 bridge where it passes over highway 55 is approximately 32'8 ". The pilot stated that he had flown the second flight lower to look for off-road landing sites to land and load new passengers. He said he did not see the wires the helicopter collided with on his initial flight, and did not see them on the accident flight until just prior to impact. The helicopter hit the wires, became uncontrollable and crashed. The fire started after ground collision. Postaccident investigation discovered no evidence of preimpact mechanical anomaly with the helicopter, and none was claimed by the pilot.