(a) The county fire marshal shall:
(1) investigate the cause, origin, and circumstances of fires that occur within the county but outside the municipalities in the county and that destroy or damage property or cause injury; and
(2) determine whether a fire was the result of negligent or intentional conduct.
(b) The commissioners court of a county, with the advice of the county fire marshal, shall adopt rules and procedures for determining which fires warrant investigation by the county fire marshal. The county fire marshal shall begin an investigation within 24 hours after the receipt of information regarding a fire that warrants investigation under commissioners court rules and procedures. The 24-hour period does not include a Sunday.

(c) In the performance of official duties, the county fire marshal, at any time of day, may enter and examine a structure where a fire has occurred and may examine adjacent premises.