As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN - ON FLIGHT 4191, SPARKING & SHORT CIRCUIT AT THE LEFT HAND UTILITY CLOSET SWITCH. CIRCUIT BREAKER TRIPPED. MAINTENANCE PLACED SYSTEM ON MEL 33-21-1. COLLARED CIRCUIT BREAKER P4 ON CIRCUIT BREAKER PANEL 1. AIRCRAFT RETURNED TO SERVICE.