The director may appoint and commission one or more investigators as the exigencies of the public service may require. Persons appointed and commissioned under this section shall have and may exercise all of the powers and authority and the benefits and privileges of a police officer or of a deputy sheriff, including the power to arrest; provided that such powers shall remain in force and effect only while in actual performance of their duties. These investigators shall consist of personnel whose primary duty is to conduct investigations as directed by the director. Persons appointed and commissioned under this section shall be exempt from chapter 76.