As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 4898 - ON THE RAMP, THE CABIN FILLED QUICKLY WITH SMOKE. CREW REPORTED LAVATORY SMOKE DETECTOR ALERTED. AIRCRAFT RETURNED TO GATE AND PASSENGERS WERE INSTRUCTED TO USE EMERGENCY EXITS. MAINTENANCE REMOVED AND REPLACED THE LEFT PACK GROUND COOLING FAN. OPERATIONAL CHECKS WERE GOOD. AIRCRAFT RETURNED TO SERVICE. (X)