What was found
(CAN) WHILE INSPECTING THE INSIDE OF THE BLADDER TANKS FOR LOOSE PATCHES BECAUSE OF LOOSE PATCHES FOUND ON ANOTHER AIRCRAFT. MAINTENANCE FOUND A BABY SLEEPER INSIDE AFT MIDDLE FUEL TANK. THIS AIRCRAFT CAME INTO THE FLEET 3 YEARS AGO AND AS THIS COMPANY DOES NOT USE OLD CLOTHS AS RAGS IT HAS BEEN IN THE AIRCRAFT FOR SOME TIME. OBVIOUSLY THERE WAS NO CLOSEUP INSPECTION DONE BEFORE. THE PANEL WENT ON AFTER MAINTENANCE LAST TIME.