As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BURNING RUBBER SMELL IN AFT CABIN CLIMBING THROUGH 7000FT LAST ABOUT 5 MIN. FWD FLIGHT ATTENDANT AND COCKPIT COULD NOT SMELL IT . NO ABNORMAL INDICATIONS IN COCKPIT. INSPECTED APU, HEAT EXCHANGERS AND RECIRCULATION FAN. NO DEFECTS NOTED. PERFORMED FULL DUCT BURNOUT PER WORKCARD 7100-2619. NO ODOR PRESENT .