Any City law enforcement officer, in addition to any other authority vested in him, has the power, upon presentation of proper credentials, to enter and inspect any dwelling, multi- family dwelling, building, structure or premises within the City as may be necessary to enforce the provisions of this chapter provided that permission is obtained from the occupant or, in the case of unoccupied property, from the owner or his agent. If such permission is refused, or is otherwise unobtainable, a search warrant must be obtained upon the showing of probable cause to believe that a violation of this chapter may exist before such entry or inspection is made.