Which type of fire investigation involves searching systematically to gather information?

The type of fire investigation that involves searching systematically to gather information is the field investigation. Field investigations are essential for fire investigators as they require a methodical approach to examine the scene of the fire, collect evidence, and analyze the circumstances surrounding the incident.

During a field investigation, the fire investigator will assess the physical evidence present, including fire patterns, burn severity, and any items that may have contributed to the fire's ignition and spread. This systematic gathering of information is critical in piecing together the sequence of events that led to the fire and helps in determining its cause.

In contrast, descriptive investigations typically focus on recounting the details of the fire rather than the systematic collection of evidence. Photo investigations rely on visual documentation to help analyze the scene but do not involve hands-on assessment. Witness investigations focus primarily on gathering statements and testimonies from those who may have observed the event, which is just one aspect of the broader field investigation process. Thus, the systematic nature and comprehensive data collection characterize the field investigation as the correct answer.