As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT AT FL260 SMOKE WAS OBSERVED COMING FROM THE RIGHT AFT AVIONICS COMPARTMENT. PILOT DECLARED AN EMERGENCY, AND LANDED WITHOUT FURTHER INCIDENT. IT WAS REPORTED THAT THE SMOKE CAUSED REDUCED VISIBILITY FOR THE FLIGHT CREW. INVESTIGATION REVEALED THE SOURCE OF THE SMOKE TO BE A DME TRANSCEIVER.