Iowa Code § 218.31: Witnesses.

In aid of any investigation, the department may summon and compel the attendance of witnesses; examine the witnesses under oath, which the director or the director’s designee may administer; have access to all books, papers, and property material to such investigation; and order the production of any other books or papers material to the investigation. Witnesses other than those in the employ of the state shall be entitled to the same fees as in civil cases in the district court.