Which of the following is NOT an obvious sign of damage during a preliminary investigation?

During a preliminary investigation, obvious signs of damage typically include visible and immediate indicators such as fire, smoke, or loss of power. Fire and smoke are direct evidence of damage or danger, indicating potential hazards that must be immediately addressed. Loss of power often suggests a systemic issue that could relate to damage in electrical systems, which is also critical information for investigators.

On the other hand, routine maintenance is generally not considered an obvious sign of damage. Instead, it refers to regularly scheduled tasks performed to ensure systems and equipment are functioning properly. Routine maintenance does not indicate a failure or damage; rather, it represents normal operational procedures that contribute to the upkeep of equipment and systems. Therefore, this option stands out as unrelated to indicators of damage in an investigative context.