As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE IN CABIN. APU WAS RUNNING FOR APPROX 5 MINS WITH BLEED OFF. NOTICED NO SMOKE. TURNED BLEED ON AND AFTER APPROX 2 MINS HAD SMOKE IN THE CABIN. LATER WE RAN BOTH ENGINES WITH NO APU AND DID NOT NOTICE ANY SMOKE. FOUND OIL IN APU AIR INLET. REMOVED WATER SOCK, CLEANED, AND CLEANED DUCT. INSTALLED WATER SEPARATOR IAW MM 12-19-02. RAN BOTH ENGINES AND SMOKE IN CABIN OR COCKPIT.