What was found
SEA - FLIGHT 2407 - THIRTY MINUTES INTO FLIGHT WHILE AT 25,000 FT, THE CABIN PRESSURE WARNING LIGHTS ILLUMINATED. THE CABIN ALTITUDE INDICATED 10,000 FT AND THE CABIN DIFFERENTIAL INDICATED 5.0 PSI. DURING DESCENT TO A LOWER ALTITUDE, THE PRESSURIZATION APPEARED TO BE NORMAL. MAINTENANCE INSPECTED THE AIRCRAFT AND FOUND THE AFT CARGO DOOR SEAL LEAKING. THE SEAL WAS REPLACED AND OPERATIONAL CHECKS WERE PERFORMED. OPERATIONAL CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.