Seoul authorities suspect that rainwater that flowed down from a mountaintop military base was the main trigger of last week's deadly landslides in southern Seoul, but further investigation is needed to find the exact cause of the disaster, the Seoul Metropolitan Government said Monday. Torrential rains sparked the mudslide at Mount Umyeon in a southern suburb of Seoul on Wednesday, which hit the lower stories of a high-rise apartment building and buried dozens of homes in hillside villages. A total of 18 residents were killed.