What was found
(CAN) ABOUT ONE MINUTE AFTER TAKEOFF THE CREW RECEIVED A LAVATORY SMOKE INDICATION IN THE COCKPIT. THERE WAS ALSO A ODOR REPORTED IN THE LAVATORY BUT NO VISIBLE SMOKE. THE SMOKE INDICATION WENT OFF AFTER ABOUT 3 MINUTES. THE ACFT RETURNED TO THE DEPARTURE AIRPORT AND MADE AN UNEVENTFUL LANDING. MAINTENANCE INVESTIGATION WAS EXTENSIVE AND FINALLY DISCOVERED A BURN MARK ON THE LAVATORY WALL BEHIND THE PASSENGER ORDINANCE SIGN. BASED ON SIMILAR DISCOLORATION DISCUSSED SL RJ-SL-25-004, OUR ENGINEERING DEPARTMENT PROVIDED AN ERVA, RJ2-3324-A13082, FOR REPAIR OF THE AREA. THIS WAS A REPEAT OCCURRENCE PREVIOUSLY DOCUMENTED ON SDR 20130219003. ORDNANCE SIGN, PN BF1-0010-005, IPC 33-24-04, FIG 1C-4.