As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE THE AIRCRAFT WAS POWERED UP ON THE GROUND, PRIOR TO A TRIP, FLIGHT MECHANIC NOTICED A LARGE AMOUNT OF WHITE SMOKE COMING FROM UNDER THE VALANCE PANEL ON LEFT SIDE OF CABIN AND ONE OF THE FLUORESCENT BULBS NOT ILLUMINATING. CIRCUIT BREAKERS FOR ALL FLUORESCENT LIGHTS WERE PULLED AS A PRECAUTION.