As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED A LAVATORY SMOKE WARNING ON EICAS WITH SMOKE IN THE CABIN SEEMING TO COME FROM THE LIGHTS. THE ACFT RETURNED TO DEPARTURE WHERE IT LANDED WITHOUT INCIDENT. MX INSPECTED THE ACFT, R & R THE NR 2 ENGINE, AND THE ACFT WAS APPROVED FOR RETURN TO SERVICE.