As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BAD ODOR COMING FROM AC SYSTEM. FOUND APU RUNNING AND EXTERNAL AIR HOOKED UP ON ARRIVAL. DISCONNECTED EXT AIR AND RAN BOTH PACKS. WALKED CABIN AND FLIGHT DK NOTICED NO BAD ODOR, NOTE TURBO PROP RUNNING ADJACENT GATE AND SUSPECT THAT WAS THE ODOR IN THE FLT DK. OK FOR SVC.