As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING FLIGHT LOUD BANGS WERE HEARD FROM THE #1 ENGINE WITH FLAMES COMING FROM THE EXHAUST STACKS. AN ENGINE FIRE DRILL WAS CARRIED OUT AND THE ENGINE SHUTDOWN. THE AIRCRAFT RETURNED TO BASE WITHOUT INCIDENT. THE ENGINE WAS REMOVED FOR INVESTIGATION. REPORT TO FOLLOW.