An investigation of each fire must be made by the officers required to report the occurrence of fires under section 18-01-06. The state fire marshal shall furnish blanks upon which reports of investigations of fires must be submitted and, when the state fire marshal deems it expedient or necessary, the state fire marshal may supervise and direct any of such investigations. Within one week after the occurrence of a fire, the officer investigating it shall furnish to the state fire marshal a written report containing a statement of the facts relating to the cause and origin of the fire and such other information as the state fire marshal may require. The state fire marshal shall keep in the state fire marshal’s office a record of all fires occurring in the state together with the facts, circumstances, and statistics in connection therewith and showing the origin of such fires as the same may be determined from the reports filed in the state fire marshal’s office.