As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON CLIMBING THROUGH FL 250 A LOUD SQUEEL STARTED AND CONTINUED THROUGH FL 370. PRESSURIZATION SEEMED NORMAL: DIFF 7.9, CABIN ALT 5900! NOT SURE WHICH SEAL ON WHICH WAS BAD. TOO LOUD TO CONTINUE FLIGHT. UPON DISCENDING THROUGH FL 250 SQUEEL STOPPED. CONTINUED TO LANDING SAFELY.