Tenn. Code Ann. § 68-102-127: Police powers of commissioner and deputies and municipal fire investigators.

(a) The commissioner of commerce and insurance and the commissioner's deputies have police powers and have the right to make arrests when necessary to preserve the law in this department, and may, in addition to investigations made by any of the commissioner's assistants, at any time make further investigations as to the origin or circumstances of any fire occurring in this state, by the appointment of special assistants or the employment of other means necessary in the commissioner's discretion.

(b) Municipal fire investigators who have been authorized by the chief of the municipal fire department or the director of fire services to conduct investigations relative to the cause and origin of fires and/or arson investigations shall also have police powers and shall have the right to make arrests when necessary to preserve the laws of this state or their respective municipalities relative to cases of arson or suspected arson.

(c) Salaried county fire investigators who have been authorized by the chief of the county-wide fire department or the director of fire services to conduct investigations relative to the cause and origin of fires or arson investigations have police powers and have the right to make arrests when necessary to preserve the laws of this state or their respective jurisdiction relative to cases of arson or suspected arson.