What was found
FLT 3387 - EN ROUTE, CARGO SMOKE LIGHT ILLUMINATED. FLIGHT CREW PERFORMED QRH, LIGHT EXTINGUISHED. AIRCRAFT RETURNED TO DTW WITHOUT INCIDENT. MAINTENANCE FOUND NR 2 CARGO FIRE BOTTLE BLOWN, REPLACED FIRE BOTTLE, SQUIB AND FIRE DETECTORS. OPS CHECK OF CARGO FIRE DETECTION IAW SF 340 26-13-00 AMM. REF: OPERATOR CONTROL NR 97ZZZX4615. (X)