During a fire scene investigation, what is the first step that should be taken?

Securing the scene to prevent contamination of evidence is essential because it establishes the integrity of the investigation. By securing the scene, investigators prevent unauthorized personnel from entering, which could alter, destroy, or compromise vital evidence related to the fire. This step is crucial because it ensures that all physical evidence, such as materials involved in the fire, burn patterns, and possible sources of ignition, remains untouched and available for analysis.

Without securing the scene first, any subsequent documentation or evidence collection could be rendered useless if the evidence has been altered or contaminated. Therefore, beginning with scene security provides a foundation for a thorough and effective investigation, allowing for accurate determinations of the fire's cause and circumstances.