Whenever it is necessary for the more effective discharge of its duties, the board of city commissioners may summon and compel the attendance of witnesses and the production of books and papers before it. The board may punish for contempt of the board with the same fines and penalties as a district judge may inflict for contempt of the district court. All process necessary to enforce the powers conferred by this section must be signed by the president of the board, attested by the city auditor, and served by any member of the police force of the city.