Except as otherwise provided in this section, an employment certificate shall be approved only by the principal of the school the child attends or by a person authorized by him or her in writing or, when there is no principal, by a person authorized by the chief administrative officer of the school or the superintendent of the school district in which the child resides, except that no person authorized by this section may approve such certificate for any child then in or about to enter his or her own employment or the employment of a firm or corporation of which he or she is a member, officer, or employee or in whose business he or she is interested. If a child who resides in an adjoining state seeks to work in Nebraska, the Department of Labor may approve the employment certificate. The officer or person approving such certificate may administer the oath provided for therein or in any investigation or examination necessary for the approval thereof. No fee shall be charged for approving any such certificate or for administering any oath or rendering any services related thereto. The school approving the employment certificate, or the department if the department has approved the employment certificate, shall establish and maintain proper records where copies of all such certificates and all documents connected therewith shall be filed and preserved and shall provide the necessary clerical services for carrying out sections 48-302 to 48-313. The person who issued the employment certificate shall report to the department any complaint concerning the conditions of employment of a child for whom a certificate is in force. Upon receipt of the report, the department shall make such investigation as it deems advisable to protect an individual child or to promote the youth-work program.