What was found
(CAN) ON A REVENUE FLIGHT, PILOTS NOTICED A FIRE WARNING FROM NR 1 ENGINE. BOTH FIRE BOTTLES WERE RELEASED AND THE ENGINE WAS SHUTDOWN. THE ACFT WAS DIVERTED BACK TO RAMP AND THE LANDING WAS UNEVENTFUL. DURING THE TROUBLESHOOTING, MECHANICS CONFIRMED THAT THE ENGINE EXHAUST SHOWS SIGNS OF DISTRESS.