Ohio Rev. Code § 3737.24
The fire marshal and the chief of the fire department of each municipal corporation in which a fire department is established, the chief of the fire department in each township in which a fire department is established, the chief of the fire department of a joint fire district, or the fire prevention officer in each township or village where no fire department is established, shall investigate the cause, origin, and circumstances of each major fire, as determined by the rules of the fire marshal, occurring in such municipal corporation, joint fire district, or township by which property has been destroyed or damaged, and shall make an investigation to determine whether the fire was the result of carelessness or design. The investigation shall be commenced within two days, not including Sunday, if the fire occurred on that day. The marshal may superintend the investigation.
An officer making an investigation of a fire occurring in a municipal corporation, joint fire district, or township shall forthwith notify the marshal, and within one week of the occurrence of the fire shall furnish him a written statement of all facts relating to its cause and origin and such other information as is required by forms provided by the marshal.
In the performance of the duties imposed by Chapter 3737. of the Revised Code, the marshal and each of his subordinates, and any other officers mentioned in this section, at any time of day or night, may enter upon and examine any building or premises where a fire has occurred, and other buildings and premises adjoining or near thereto.
R.C. §3737.24