In making investigations pursuant to § 27-31, the fire marshal may issue a summons directed to a sheriff or sergeant of any county, city or town commanding the officer to summon witnesses to attend before him at such time and place as he may direct. Any such officer to whom the summons is delivered, shall forthwith execute it, and make return thereof to the fire marshal at the time and place named therein. Witnesses, on whom the summons before mentioned is served, may be compelled by the fire marshal to attend and give evidence, and shall be liable in like manner as if the summons had been issued by a magistrate in a criminal case. They shall be sworn by the fire marshal before giving evidence, and their evidence shall be reduced to writing by him, or under his direction, and subscribed by them respectively.