It shall be the duty of the Attorney General of the United States immediately to inquire into the facts of cases reported to him by customs officers and the laws applicable thereto, and if it appears probable that any fine, penalty, or forfeiture has been incurred by reason of such ¹ violation, for the recovery of which the institution of proceedings in the United States district court or the Court of International Trade is necessary, forthwith to cause the proper proceedings to be commenced and prosecuted, without delay, for the recovery of such fine, penalty, or forfeiture in such case provided, unless, upon inquiry and examination, the Attorney General decides that such proceedings can not probably be sustained or that the ends of public justice do not require that they should be instituted or prosecuted, in which case he shall report the facts to the Secretary of the Treasury for his direction in the premises.