As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU RUNNING PRIOR TO BOARDING WITH APU BLEED AND PACKS ON. A HAZE WAS IN THE CABIN WITH A MUSTY ODOR. HAZE DISSIPATED BUT ODOR REMAINED. MAINTENANCE COMPLIED WITH NO GO ODI AND AFTER TROUBLESHOOTING FOUND AN OIL LEAK AT THAT APU GENERATOR. REMOVED AND REPLACED APU GENERATOR, CLEANED AND DECONTAMINATED COMPARTMENT. RAN PACKS. NO ODOR PRESENT.