As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BWI - CREW REPORTED CARGO DOOR WARNING INDICATION ON CLIMBOUT. EMERGENCY DECLARED RETURNED BWI LANDED WITHOUT INCIDENT. FOUND METAL HOOK IN MICRO SWITCH. REMOVED OBSTRUCTION AND AFT CARGO DOOR LIGHT WENT OUT. SYSTEM GROUND CHECKED NORMAL OPERATION.