As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT, THE CREW RECEIVED A LAV SMOKE WARNING MESSAGE ON THE EICAS DISPLAY. THIS WAS ACCOMPANIED BY A HAZE OR SMOKE WITH CONDENSATION COMING FROM THE LAVATORY AREA AND THE PACKS BY A DEAD HEADING CREW MEMBER. THE CREW RETURNED TO DEPARTURE AND DECLARED AN EMERGENCY AND PROCEEDED TO LAND WITHOUT INCIDENT. MX PERSONNEL ASSESSED THE ACFT AND REPLACED THE LAVATORY SMOKE DETECTOR. ALL OPS CHECKS PROVED SATISFACTORY AND NO OTHER ACTIONS WERE REQUIRED.