As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMBOUT THE COCKPIT FILLED WITH SMOKE. THE AIRCRAFT DECLARED AN EMERGENCY AND RETURNED TO THE AIRPORT. THE SMOKE WAS OBSERVED COMING FROM F/O'S SIDE. AFTER AIRCRAFT RETURNED TO GATE, MECHANIC FOUND P6-12 CIRCUIT BREAKER WITH EVIDENCE OF BEING OVERHEATED AND TERMINAL CONNECTOR BURNED.