(1) The responsibility for investigating the origin, cause, circumstances, and extent of loss of all fires shall be assigned as follows:
(a) Within any city or town, the chief of the fire department;
(b) Within unincorporated areas of a county, the county fire marshal, or other fire official so designated by the county legislative authority.
(2) No fire marshal, or other person, may enter the scene of an emergency until permitted by the officer in charge of the emergency incident.
(3) Nothing shall prevent any city, town, county, or fire protection district, or any combination thereof, from entering into interlocal agreements to meet the responsibility required by this section.
(4) When any fire investigation indicates that the cause of the fire is determined to be suspicious or criminal in nature, the person responsible for the fire investigation shall immediately report the results of said investigation to the local law enforcement agency and the chief of the Washington state patrol, through the state fire marshal.
(5) In addition to the responsibility imposed by this section, any law enforcement agency, sheriff, or chief of police may assist in the investigation of the origin, cause, circumstances, and extent of loss of all fires within his or her respective jurisdiction.
(6) The chief of the Washington state patrol, through the director of fire protection or his or her deputy, may investigate any fire for the purpose of determining its cause, origin, and the extent of the loss. The chief of the Washington state patrol, through the director of fire protection or his or her deputy, shall assist in the investigation of those fires of criminal, suspected, or undetermined cause when requested by the reporting agency. In the investigation of any fire of criminal, suspected, or undetermined cause, the chief of the Washington state patrol and the director of fire protection or his or her deputy, are vested with police powers to enforce the laws of this state. To exercise these powers, authorized deputies must receive prior written authorization from the chief of the Washington state patrol, through the director of fire protection, and shall have completed a course of training prescribed by the Washington state criminal justice training commission.