As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FAT- FLIGHT 4299. DURING CLIMB RECEIVED A LAV SMOKE WARNING MESSAGE. HAPPENED TWO TIMES, FOR 30 SECONDS EACH. RETURNED TO THE FIELD AND ACCOMPLISHED A UNEVENTFUL LANDING. NO SMOKE OR FIRE NOTICED. MAINTENANCE FOUND THE SOURCE TO BE THE APU. PLACED THE APU ON MEL 49-10-1B. RAN ENGINES FOR TWO HOURS AT ELEVATED BLEED TEMPS TO CLEAR SMELL. AIRCRAFT RETURNED TO SERVICE.