As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - ON GROUND, SMOKE IN CABIN AFTER APU STARTED AND PACKS TURNED ON. FOUND HYDRAULIC LEAK AROUND RIGHT ENGINE THRUST REVERSER CONTROL VALVE. REPLACED PIPE ASSEMBLY FOR HYDRAULIC LEAK AROUND RIGHT ENGINE THRUST REVERSER CONTROL VALVE. REPLACED THE APU ASSEMBLY DUE TO HYDRAULIC FLUID INGESTION. SYSTEM GROUND CHECKED NORMAL OPERATION.