An investigation report released by Japan's Fire and Disaster Management Agency highlights the role of vacant houses in exacerbating a large-scale fire that occurred in Oita City in November of last year. The cause of the fire remains undetermined, as significant damage rendered most identifiable evidence untraceable. The report outlined how the presence of many unoccupied buildings in the vicinity may have delayed detection and contributed to the fire's escalation, notably including two adjacent vacant houses to the origin site.

The initial call to emergency services did not come from the affected building, where residents lost their lives, but rather from a nearby location approximately 100 meters away, noting visibility of flames in the west. The first responding firefighters reported flames heightening from the residential origin, which had spread to nearby vacant houses on both the eastern and southern flanks. In total, the fire affected 196 structures, with a significant number being unmaintained vacant properties, which may have posed additional risks due to overgrown vegetation and broken roofing tiles.

The fire department's conclusion identified the fire's origin as occurring indoors on the east side of the building. Although potential ignition sources included tobacco, electrical appliances, indoor wiring, and arson, the advanced state of destruction left no conclusive evidence for pinpointing the cause. Consequently, the report concluded the origin of the fire remains classified as unknown, underscoring ongoing concerns regarding fire safety in areas with numerous abandoned structures that can threaten nearby inhabited homes.