Section 128G. The department shall annually inspect all farm labor camps as defined in the state sanitary code, or, in lieu thereof, may delegate any such annual inspection to a local board of health. When such inspection is so delegated, the local board of health shall make its inspection and file its report with the department within thirty days of notice of such delegation. If a farm labor camp after inspection conforms with the requirements of said code the department shall issue a certificate of occupancy which shall be posted upon one or more of the buildings comprising such camp. No such camp shall be opened in any year unless a current certificate of occupancy has been so posted. Any such certificate may be revoked for any violation of said code which the department after inspection determines exists. Complaints in writing of violations of the sanitary code, whether filed with the local board of health or the department, shall be investigated by the department as soon as practicable but in any event within thirty days after such filing. If any such complaint is filed with the local board of health said board shall forthwith forward said complaint to the department. The provisions of this section shall not be construed to limit or restrict the powers and duties of local boards of health.