As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING INITIAL CLIMBOUT OF PHL THE CABIN AND COCKPIT BEGAN TO FILL WITH SMOKE AND A LAV SMOKE MESSAGE WAS DISPLAYED ON EICAS. THE AIRCRAFT RETURNED TO PHL AND LANDED WITHOUT INCIDENT. MAINTENANCE RAN THE ENGINES AT FULL POWER AND COULD NOT DUPLICATE THE FAULT. THE AIRCRAFT WAS THEN FERRIED TO CMH FOR FURTHER TROUBLESHOOTING. IN CMH THE AFT SUMP IN E2 WAS FOUND TO BE LEAKING AND THE ENGINE WAS REPLACED WITH NO FURTHER DEFECTS NOTED.