In furtherance of any such investigation, inspection or hearing, the Commissioner or his duly authorized agent shall have full authority to make any and all necessary investigations relative to the complaint or matter being investigated; and they shall have free and unimpeded access during normal business hours to all buildings, yards, warehouses, storage and transportation facilities in which grain is kept, stored, handled, or transported, or where records of grain transactions are kept. (1973, c. 665, s. 12.)