What was found
PRIOR TO BOARDING, AFT FLIGHT ATTENDANT REPORTED TRACE AMOUNTS OF SMOKE IN CABIN. APU BLEED & APU WERE TURNED OFF AND THE TRACE AMOUNT OF SMOKE DISSAPATED. AIRCRAFT WAS GROUNDED. MAINTENANCE ACCOMPLISHED TASK CARDS 26L00002001 & JCJC26L00002002 AND FOUND NO EVIDENCE OF APU BLEED AIR, PACKS, GALLEY OVENS, COFFEE MAKERS OR ELECTRICAL ODORS.