As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE TO MDW, CREW STARTED APU AT FL250; APU FIRE LIGHT ILLUMINATED FOR APPROX 5-10 SECONDS. FIRE LIGHT EXTINGUISHED WITH NO CREW ACTION, ACCOMPLISHED QRH FOR APU FIRE. FIRE HANDLE PULLED; BOTTLE NOT DISCHARGED. INSPECTED APU FIRE LOOPS, NO DEFECTS NOTED. RERACKED FIRE DETECTION BOX PER M/M. SYSTEM OPS CHECK NORMAL.