42 U.S. Code § 3611 - Subpoenas; giving of evidence
The Secretary may, in accordance with this subsection, issue subpoenas and order discovery in aid of investigations and hearings under this subchapter. Such subpoenas and discovery may be ordered to the same extent and subject to the same limitations as would apply if the subpoenas or discovery were ordered or served in aid of a civil action in the United States district court for the district in which the investigation is taking place.
Witnesses summoned by a subpoena under this subchapter shall be entitled to the same witness and mileage fees as witnesses in proceedings in United States district courts. Fees payable to a witness summoned by a subpoena issued at the request of a party shall be paid by that party or, where a party is unable to pay the fees, by the Secretary.