((a)) The Secretary may make such investigations as the Secretary deems necessary to carry out effectively the Secretary’s responsibilities under this chapter or to determine whether a person has engaged or is engaging in any acts or practices that constitute a violation of any provision of this chapter, or of any plan or regulation issued under this chapter. For the purpose of an investigation, the Secretary may administer oaths and affirmations, subpoena witnesses, compel their attendance, take evidence, and require the production of any books, papers, and documents that are relevant to the inquiry. The attendance of witnesses and the production of records may be required from any place in the United States. In case of contumacy by, or refusal to obey a subpoena issued to, any person, including a handler (or an importer who is subject to the plan), the Secretary may invoke the aid of any court of the United States within the jurisdiction of which such investigation or proceeding is carried on, or where such person resides or carries on business, in requiring the attendance and testimony of witnesses and the production of books, papers, and documents; and such court may issue an order requiring the person to appear before the Secretary, there to produce records, if so ordered, or to give testimony touching the matter under investigation. Any failure to obey such order of the court may be punished by the court as contempt thereof. All process in any such case may be served in the judicial district in which the person is an inhabitant or wherever the person may be found. The site of any hearing held under this subsection shall be within the judicial district in which the person is an inhabitant or in which the person’s principal place of business is located.

((b)) No person shall be excused from attending and testifying or from producing books, papers, and documents before the Secretary, or in obedience to the subpoena of the Secretary, or in any cause or proceeding, criminal or otherwise, based on, or growing out of, any alleged violation of this chapter, or of any plan or regulation issued thereunder, on the grounds that the testimony or evidence, documentary or otherwise, required of the person may tend to incriminate the person or subject the person to a penalty or forfeiture. However, no person shall be prosecuted or subjected to any penalty or forfeiture on account of any transaction, matter, or thing concerning which the person is compelled, after having claimed the person’s privilege against self-incrimination, to testify or produce evidence, documentary or otherwise, except that any individual so testifying shall not be exempt from prosecution and punishment for perjury committed in so testifying.