As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB THE FLIGHT CREW GOT AN APU FIRE INDICATION. AIRCRAFT RETURNED TO STL. MAINTENANCE PERFORMED AN APU FIRE INSPECTION. NO EVIDENCE OF FIRE WAS NOTED. INSPECTED APU COWLING AND NO DAMAGE WAS NOTED. MAINTENANCE DEFERRED THE APU FIRE DETECTION SYSTEM AND THE APU.