What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS CAB ALT WARNING ILLUMINATED AND SOUNDED AS AIRCRAFT PASSED 12,000. LEVELED AT 13,000 THEN DECENDED TO 10,000. CAB ALT WARNING EXTINGUISHED AT @ 8,500 AIRCRAFT ALT. AIRCRAFT FELT A LITTLE GENTLE BUFFETING THROUGHOUT FLIGHT. EMERGENCY DECLARED, RETURNED TO STL. FLIGHT ATTENDANTS REPORTED SLIGHT HAZE IN CABIN. MAINTENANCE ACCOMPLISHED BITE CHECK OF BOTH CABIN PRESSURE CONTROLLERS, NO FAULTS FOUND. ACCOMPLISHED GROUND PRESSURIZATION TEST IAW AMM 21-31-00. ALL TESTS NORMAL. A/C OK FOR SERVICE.