As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE IN CABIN WHILE ON THE GROUND, PARKED AT THE GATE WITH APU PACKS ON, AN OIL ODOR AND FUMES ENTERED THE CABIN. THE APU WAS SHUTOFF AS A PRECAUTIONARY MEASURE. THIS SITUATION HAD OCCURRED ON LEGS PRECEDING THIS ONE. THE APU WAS REPLACED AND FORWARDED FOR REPAIRS.