What was found
ON CLIMBOUT FROM LFT-MEM WE HAD A MAIN CARGO MIDDLE SMOKE DETECTOR LIGHTS 2,3,4 ILLUMINATE . NO OTHER INDICATIORS OF SMOKE OR FIRE, DECLARED EMERGENCY, RETURNED TO LFT RAN QRC & QRH STOPPED ON RUNWAY, EMERGENCY CREW SAW AND DETECTED NO FIRE OR SMOKE INDICATIONS. AMM: 26-16-30-4 REMOVED AND REPLACED MID 2, MID 3, & MID 4 MAIN CARGO COMPARTMENT SMOKE DETECTORS IAW AMM 26-16-30-4 OPS CHKD GOOD.