As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON APU START AT KCLE, THE CABIN AND COCKPIT FILLED WITH SMOKE. FLIGHT CREW NOTIFIED ATC AND ASKED FOR CFR. THE AIRCRAFT WAS EVACUATED WITHOUT INCIDENT. CFR FOUND NO EVIDENCE OF FIRE. MAINTENANCE DETERMINED THE SMOKE WAS PRODUCED BY THE APU. THE APU WAS DEFERRED AND THE AIRCRAFT WAS RELEASED FOR SERVICE. THE APU WILL BE REMOVED AT THE FIRST OPPORTUNITY.