Pub. L. 92-340, tit. I, sec. 103

Sec. 103. The Secretary may investigate any incident, accident, or act involving the loss or destruction of, or damage to, any structure subject to this title, or which affects or may affect the safety or environmental quality of the ports, harbors, or navigable waters of the United States. In any investigation under this title, the Secretary may issue a subpena to require the attendance of any witness and the production of documents and other evidence. In case of refusal to obey a subpena issued to any person, the Secretary may request the Attorney General to invoke the aid of the appropriate district court of the United States to compel compliance. Witnesses may be paid fees for travel and attendance at rates not exceeding those allowed in a district court of the United States.