What was found
WHILE AT CRUISE FL280, RECEIVED FORWARD CARGO SMOKE INDICATION. THE MASTER WARNING ILLUMINATED ACCOMPANIED WITH A FIRE BELL. COMPLIED WITH COM PROCEDURES AND DISCHARGED BOTH EXTINGUISHER BOTTLES INTO THE FORWARD CARGO AREA. NO SMOKE EVER IN CABIN OR COCKPIT. AN EMERGENCY WAS DECLARED AND THE FLIGHT DIVERTED TO BUF. LANDING WAS UNEVENTFUL EXCEPT AIRCRAFT WAS MET BY CFR EQUIPMENT. NO EVIDENCE OF SMOKE OR FIRE WAS FOUND. MAINTENANCE TESTED BOTH DETECTION AND SUPPRESSION SYSTEMS IN THE CARGO AREAS AND FOUND NO DISCREPANCIES. REPLACED BOTH FORWARD AND AFT CARGO AREA FIRE EXTINGUISHING BOTTLES. OPERATIONAL CHECK OK. AIRCRAFT RETURNED TO SERVICE.