On December 12, 1994, at 0900 central standard time, an Aerospatiale ATR 72-212, N633AS, sustained minor damage while taxiing at the Dallas/Fort Worth International Airport, Texas, (DFW). There were no injuries to the 4 crewmembers and the 34 passengers aboard the airplane. Visual meteorological conditions prevailed for the scheduled 14 CFR Part 121 flight. The airplane was being operated by Atlantic Southeast Airlines as ASA Flight 7694, on a scheduled domestic passenger service from DFW to Oklahoma City, Oklahoma. According to the operator, the airplane was holding short of the runway for departure, when the flight crew heard a noise followed by the illumination of the #1 generator fault light. The crew contacted dispatch and related the events to their maintenance personnel. While taxiing back to the gate for further troubleshooting, the fire warning light for the number one engine illuminated and smoke was observed coming from the engine. The crew discharged both onboard fire bottles and secured the engine. An emergency evacuation was ordered by the flight crew on taxiway alpha via the right aft service door. There were no reported injuries during the evacuation. A post- incident inspection of the affected engine by a Federal Aviation Administrator inspector confirmed minor damage and evidence of fire due to the internal failure of the #1 DC starter-generator. The failed component, part number 8260-121, serial number 8260- 121, serial number 1232, had accumulated a total of 646.6 hours since last overhaul, and 2,992 hours since new. A teardown confirmed that the internal failure was the result of the failure of a generator bearing.