As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PRIOR TO DEPARTURE THE ACFT BEHIND US REPORTED THAT THE APU HAD A FIRE IN THE TAILPIPE & RECOMMENDED THAT WE EXTINGUISH IT. CFR WAS CALLED OUT & SAID IT WAS STILL BURNING & TOLD US TO FIRE THE APU FIRE BOTTLE, WHICH WE DID & AT THAT TIME FIRE WAS REPORTED OUT & RETURNED TO GATE. ACCOMPLISHED INSPECTION OF APU IAW 49-00-00-200-001-A, NO DEFECT NOTED. REPLACED APU FIRE EXTINGUISHING BOTTLE.