What was found
AT FL 240, CARGO SMOKE LIGHT ILLUMINATED. ALL CREW MEMBERS SMELLED SMOKE. PERFORMED SMOKE SOURCE IDENT CHECKLIST. INSPECTED FOR SOURCE, INSPECTED CARGO, CARGO COMPT, E/E COMPT, LOWER CARGO COMPTS AND AFT AIRSTAIRS AREA. RAN ENGINES, RAN A/C PACKS AND GASPER SYSTEMS. USED DIFFERENT BLEED COMBINATIONS, OPS CHECK SMOKE SYSTEM. UNABLE TO DUPLICATE OR FIND SOURCE OF SMOKE.