As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOST CABIN PRESSURE AT FL310 AND PERFORMED AN EMERGENCY DESCENT TO 10,000 FEET. THE OUTFLOW VALVE WAS FULLY CLOSED AND BOTH SUPPLY PRESSURES INDICATED 25 PSI. FLIGHT LANDED WITHOUT INCIDENT AT GFK. AFTER LANDING, THE CREW DETERMINED THERE WAS NO AIRFLOW FROM THE LEFT PACK AND NORMAL AIRFLOW FROM THE RIGHT PACK MAINTENANCE SECURED A LOOSE DUCT IN THE TAIL. AIRCRAFT RETURNED TO SERVICE.