The Maine fire marshal’s office has confirmed that a propane leak was to blame for a blast that leveled a two-unit apartment building and killed one person. Fire investigators said the leak was in the wall of the unit next to one where a woman’s body was found in the rubble Tuesday in Bath. Investigators believe fumes seeped into a crawl space before being ignited by an unknown source. The blast flattened the building, awakened neighbors, and scattered debris as far as a quarter-mile away. Four people were taken to the hospital.