After taking and filing the oath of office, the commissioner has authority to issue subpoenas for persons and subpoenas duces tecum and to administer oaths to witnesses the same as is conferred upon district judges. The subpoenas may be directed to any sheriff, or chief of police, who immediately shall serve the subpoenas. The officer is entitled to such fees as are allowed to sheriffs for serving subpoenas in district court. The fees must be paid in the same manner as is provided in this chapter for witness fees and commissioner’s fees. The commissioner may punish for contempt in the same manner as the district court.