Whenever an employer or his insurance carrier and an injured employee, or the dependents of a deceased employee, shall, by agreement, duly signed, settle upon and determine the compensation due to the injured employee, or to the dependents of a deceased employee, as provided by law, the employer or the insurance carrier shall forthwith file with the bureau a true copy of the agreement. The agreement shall not bind the employer or injured employee, or the dependents of a deceased employee, unless approved by the bureau. If an agreement for lawful and adequate compensation, approved by the bureau, is not filed within twenty-one days after the date of the happening of the injury, the bureau shall, so far as practicable, endeavor to bring about a settlement of the pending claim. If no petition is filed by the injured employee, or the dependents of a deceased employee, the bureau may institute an inquiry on its own motion, to determine the reasons for the failure to agree as to compensation, and may, either before or after the institution of the inquiry, with the consent of the injured employee, or the dependents of a deceased employee, file a petition for compensation. When such petition is filed by said bureau, on its own initiative, the subsequent proceedings shall be the same as is hereinafter set forth in cases where the claimant files a petition.