What was found
CAPTAIN REPORTED SMOKE IN CABIN ON GROUND WITH FORWARD AND AFT LAV SMOKE MASTER WARNING. CONTRACT MX INSPECTED AFT EQUIPMENT BAY EQUIPMENT AND DUCTING FOR INTEGRITY AND FOUND NO DEFECTS, INSPECTED AND OPS CHECKED BOTH FORWARD AND AFT LAV SMOKE DETECTORS AND OPS CHECKED NORMAL. PERFORMED APU NORMAL START AND LT & RT PACK OPERATION WITH NO REPEAT OF CABIN SMOKE. ACCOMPLISHED TWICE WITH NO REPEAT, NO FAULTS FOUND RETURNED TO SERVICE.