There is established within the department a bureau of field services, under the direction and supervision of a deputy director in charge of field services, who shall be appointed by the director and who shall be within the state civil service. The deputy director shall direct and supervise the work of the bureau of field services and shall formulate methods of investigation and supervision and develop various processes in the technique of supervision by the parole staff. The deputy director is responsible for all investigations of persons eligible for release from state penal institutions, and for the general supervision of persons released from penal institutions. The deputy director in charge of the bureau of field services is responsible for the collection and preservation of records and statistics with respect to paroled prisoners as may be required by the director and the chairperson of the parole board. The deputy director shall employ parole officers and assistants as may be necessary, subject to the approval of the director. The deputy director shall select secretarial and other assistants as may be necessary and may obtain permanent quarters for the staff as may be necessary.