What was found
DURING FLIGHT, THE CARGO SMOKE WARNING LIGHT ILLUMINATED, CARGO IRE EXTINGUISHER SWITCHED ON, CARGO SMOKE WARNING LIGHT WENT OUT SHORTLY AFTER, QRH COMPLETED. AIRCRAFT RETURNED TO MSP, LANDED WITHOUT DISCREPANCY. MAINTENANCE INSPECTED CARGO COMPARTMENT AND DETERMINED TO BE INDICATION PROBLEM. MX REPLACED CARGO SMOKE DETECTOR IAW 26-13-15 AMM. OPS CHECK GOOD. REPLACED FIRE BOTTLE AND CARTRIDGE, FUNCTIONAL TEST GOOD.