As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT 6,000 FEET, MAIN DECK CARGO DOOR LIGHT AND AURAL WARNING APPEARED, WHILE RETURNING TO THE AIRPORT, THE WARNING EXTINQUISHED AT 4,000 FEET. LANDED WITH OUT FURTHER INCIDENT. AIRCRAFT WAS GROUNDED BY MAINTENANCE. MAINTENANCE CYCLED MCD OPEN AND LOCK SWITCHES IAW IAI SUPP 52-32-00. ALL SYSTEMS OPERATE NORMAL. VISUALLY VERIFIED ALL MCD LOCKS IN LOCKED POSITION. AIRCRAFT RETURNED TO SERVICE.