As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN PACKS TURNED ON CABIN FILLED WITH BLUE HAZY SMOKE. APU BLEED AIR WAS TURNED OFF, RAN APU/PACKS SEVERAL HRS-NO SMOKE OR FUMES NOTED IN CABIN. ALSO NO EXTERNAL OIL LEAKS NOTED. AS A PRECAUTION REPLACED APU PER M/M. OPS AND LEAK CHECK OK.