7 U.S. Code § 4816 - Investigations
The Secretary may make such investigations as the Secretary considers necessary—
(b) Oaths and affirmations; subpenas
(1) For the purpose of such investigation, the Secretary may administer oaths and affirmations, subpoena witnesses, compel their attendance, take evidence, and require the production of any records that are relevant to the inquiry.
(c) Judicial enforcement; contempt proceedings; service of process
(1) In the case of contumacy, or refusal to obey a subpoena, by a person, the Secretary may invoke the aid of a court of the United States with jurisdiction over such investigation or proceeding, or where such person resides or does business, in requiring the attendance and testimony of such person and the production of such records.
(2) The court may issue an order requiring such person to appear before the Secretary to produce records or to give testimony touching the matter under investigation.
(3) A failure to obey an order issued under this section by the court may be punished by the court as a contempt thereof.