((a)) In carrying on the work herein authorized, the Secretary of Agriculture, or any officer or employee designated by him for such purpose, shall have power to hold hearings, administer oaths, sign and issue subpenas, examine witnesses, take depositions, and require the production of books, records, accounts, memoranda, and papers, and have access to office and warehouse premises. Upon refusal by any person to appear, testify, or produce pertinent books, records, accounts, memoranda, and papers in response to a subpena, or to permit access to premises, the proper United States district court shall have power to compel obedience thereto.
((b)) Witnesses summoned before the Secretary or any officer or employee designated by him shall be paid the same fees and mileage that are paid witnesses in the courts of the United States, and witnesses whose depositions are taken and the persons taking the same shall severally be entitled to the same fees as are paid for like service in the courts of the United States.