Investigators are called to fire scenes by Operations companies or the police department when the cause of a fire is not immediately identifiable or when the fire is determined to be a criminal act.

Investigators use a variety of techniques and strategies to identify the source and cause of fires. They examine burn patterns, inspect debris at the scene, and interview victims and witnesses during the course of an investigation. The investigators' primary goal is to determine the cause and origin of any fire that requires their response. They do this by conducting an examination of the fire scene and then carefully evaluating all pertinent information gathered during an investigation. If the fire event is determined to be a criminal act, AFD investigators are also responsible for conducting the criminal investigation of the fire and making subsequent arrest of the person(s) responsible.

Some of the other investigative resources that AFD uses during an investigation include a Texas-licensed, polygraph examiner, and certified accelerant detection canines named Max and Smokey, who can locate traces of ignitable liquids and other materials that indicate that a fire may have been intentionally set. AFD investigators have an outstanding record of determining fire causes. In 2015, causes were determined for more than 60% of structure and automobile fires, and arrest were made for 37% of fires determined to be arson.