What was found
(CAN) AFTER PASSENGER DISEMBARKATION SMOKE WAS OBSERVED IN THE COCKPIT. THE APU WAS RUNNING, ACCORDING TO MAINTENANCE PERSONNEL AND LEFT PACK AIR CYCLE MACHINE IS DEFECTIVE. SHUT OFF THE APU IMMEDIATELY AND NORMAL INDICATIONS WERE OBSERVED. AT THE EVENT AIRPORT FIRE BRIGADE WERE CALLED AS A PRECAUTION AND THE SMOKE DISAPPEARED 10 MINUTES LATER.