What was found
(CAN) DURING CLIMB, AT FL70, AN ENGINE FIRE OCCURRED UNDER UNKNOWN CIRCUMSTANCES. A PASSENGER ON BOARD THE ACFT TOOK A PICTURE OF THE ENGINE SHOWING FLAMES EXTERNAL TO THE NACELLE. THE CREW IMMEDIATELY SHUT THE ENGINE DOWN AND RETURNED TO THE DEPARTURE AIRPORT WHERE AN UNEVENTFUL SINGLE ENGINE LANDING WAS MADE. MFG FIELD SUPPORT REPRESENTATIVE WILL BE ON SITE TO ASSIST IN THE PRELIMINARY INVESTIGATION.