On 06 NOV 09, the Commander and his crew, on board the Boeing 737-500 aircraft, registration LV-BIM, performing the international scheduled Aerolineas Argentinas flight 1244, a Boeing 737-53A, took off from Buenos Aires/Ezeiza Airport (SAEZ) After takeoff and crossing FL 90, the auxiliary power unit (APU) fire alarm went off; immediately the crew performed the corresponding emergency procedures and the alarm was extinguished. Subsequently, the Commander decided to return to the departure airport, at which time the APU fire alarm came on again. He declared an emergency and requested priority for landing. The Air Traffic Control Tower Operator (TWR) EZE, authorized the instrument approach procedure for runway 11, and the approach and landing were carried out safely. After landing, the alarm went off and the aircraft was stopped on the runway. The fire services visually verified that there was no fire in the affected area; therefore, the aircraft was rolled to the main apron, position No. 15, where the passengers deplaned without any inconvenience. Cause During an international passenger flight, after takeoff, in the climb phase, APU fire alarm ignition, return to the departure airport and emergency landing, due to simultaneous failure of both fuel shut-off valves, resulting in overheating and burning of wiring and pipe covering. Contributing factors: 1) Electrical failure in the induction coil of the shut-off valve P/No. AV16E1209D. 2) Failure of a seal and its housing in valve P/Nr. V5000.