33 U.S.C. § 1523
General procedures; issuance and enforcement of orders; scope of authority; evidentiary matters
The Secretary or his delegate shall have the authority to issue and enforce orders during proceedings brought under this chapter. Such authority shall include the authority to issue subpenas, administer oaths, compel the attendance and testimony of witnesses and the production of books, papers, documents, and other evidence, to take depositions before any designated individual competent to administer oaths, and to examine witnesses.