As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FPO/FPO - FLT 410 - PILOT REPORT: RIGHT FIRE PULL HANDLE ILLUMINATES IN-FLIGHT. PILOT DECLARED AN EMERGENCY AND RETURNED TO FPO AND LANDED WITHOUT INCIDENT. MAINTENANCE REPORT: CLEANED AND DRIED PHOTO CELLS, OPERATIONAL CHECK NORMAL. SUSPECT MOISTURE FROM RAIN STORM MAY BE THE CAUSE.