As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND TEH AIRCRAFT RETURNED TP PHL DUE TO A STRONG ODOR FUMES AFTER TAKEOFF. ODOR GOT STRONGER IN CLIMB. FLIGHT ATTENDANTS STATED ODOR WAS STRONGER IN REAR OF AIRCRAFT. ODOR WAS STRONG IN FLIGHT DECK. THE AIRCRAFT LANDED SAFELY AT PHL WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND THE APU STARTER LEAKING OIL AND REPLACED THE O-RING PER AMM 49-42-51. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED WITH NO ODORS NOTED.