What was found
BNA - FLT 4539 - PILOT REPORTS: ON TAKEOFF, THE LEFT ENGINE FIRE WARNING LIGHT ILLUMINATED FOLLOWED BY A LOUD NOISE FROM THE LEFT ENGINE. DISCHARGED ENGINE FIRE BOTTLES AS A PRECAUTIONARY MEASURE. CREW ABORTED TAKEOFF. AS THEY WERE RETURNING TO THE GATE, THE CFR STOPPED THE A/C AND TOLD CREW THAT THERE WAS RESIDUAL FLAMES. PASSENGERS WERE DEPLANED ON THE RAMP WITH NO INJURIES. C/A - VERIFIED THERE WERE NO FLAMES IN THE ENGINE NACELLE, REPLACED ENGINE FIRE BOTTLES AND LEFT ENGINE.