As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GNDED. A VERY LOUD SQUEAL FROM THE L1 DOOR WAS REPORTED & THE FLIGHT CREW DECLARED AN EMER & RETURNED. FOUND THE L1 DOOR PRESS SEAL CUT & LEAKING IN THE UPPER FWD CORNER OF THE DOOR. REPLACED THE DEFECTIVE PRESS SEAL & ACCOMPLISHED A SATISFACTORY LEAK CHECK IAW AMM 52-09-01.