The following New Hampshire State Laws determine the responsibility of the investigation of fires, building collapse, and carbon monoxide releases.
RSA 153:4-a Duties of Fire Marshal
The State Fire Marshal shall also assist several counties, cities, town, village districts, and precincts in supervising and enforcing local laws, bylaws, and ordinances where existent, relative to the investigation of the cause, origin, and circumstance of fires.
RSA 153:11 Report of Causes and Origins of All Fires
When the cause, origin, and circumstances of any fire occurring in any city, town, village, district, or precinct in this state indicates that such fire was the result of design, or of suspicious origin, the fire chief shall immediately notify the State Fire Marshal. The State Fire Marshal shall have the option and authority to submit his or her finding of facts in the case to the state police, country attorney or local authorities who my assist him in the matter of arrest and prosecution.
RSA 153:12 Fire Chiefs
Any fire chief may request the state fire marshal at any time to assist him in ascertaining the cause, origin, and circumstances relative to any fire within his territorial jurisdiction.
RSA 153:18 Investigations
Any fire, building collapse, or release of carbon monoxide other than that from a motor vehicle occurring where death results shall be reported immediately to the Office of the State Fire Marshal by the fire chief, and the Office of the State Fire Marshal shall investigate the fire, building collapse, or release of carbon monoxide within 48 hours after receiving said report.
RSA 154:7-a Fire Investigations
The fire officer in charge or his or her designee shall investigate the cause and origin of fires.