Wiktionary
n. (context US English) A public official with police powers responsible for enforcing fire safety regulations, and sometimes, who also investigates suspicious fires.
WordNet
n. the head of a fire department [syn: fire chief]
Wikipedia
A fire marshal, in the United States and Canada, is often a member of a fire department but may be part of a building department or a separate department altogether. Fire marshals' duties vary but usually include fire code enforcement and/or investigating fires for origin and cause. Fire marshals may be sworn law-enforcement officers and are often experienced firefighters.
A fire marshal's duties vary by location. Fire marshals may carry a weapon, wear a badge, wear a uniform or plain clothes, and make arrests pertaining to arson and related offenses, or, in other localities, may have duties entirely separate from law enforcement, including building- and fire-code-related inspections. In many areas, the fire marshal is responsible for enforcing laws concerning flammable materials.
Usage examples of "fire marshal".
Later, after the fire was out, the fire marshal had come and questioned some kids who had been in the cafeteria.
The fire marshal called out to a nearby member of his department, who called back they'd found that one atop some bedsprings in the stairwell.
When the police and fire crews had arrived, most of the action was over, and the fire marshal had been worked up into a lather over the deaths.
I'm going to question some more witnesses, and the fire marshal sent all the evidence to the state crime lab.