As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER TAKEOFF, THE CREW REPORTED SMOKE IN THE CABIN AND RETURNED TO FIELD. UPON LANDING, THE CREW DISCHARGE THE APU FIRE BOTTLE. AFTER FURTHER TROUBLESHOOTING, THE SITUATION WAS DUPLICATED AND IT WAS REPORTED THAT THE APU OIL COOLER WAS CLOGGED. REMOVED AND REPLACED OIL COOLER OPS CHECK GOOD.