When any county establishes a retirement plan under the provisions of this chapter, there shall be created in the treasury of the county and opened upon the books of the auditor and treasurer of the county, a trust fund to be known as the “peace officers and fire service retirement fund” for the payment of administration expense and retirement, disability and death benefit allowances. Said fund shall consist of all moneys paid into said fund in accordance with the provisions of this chapter and of the ordinance creating the retirement plan and earnings from investments. The board of administration shall have exclusive control of the administration, investment and reinvestment of said fund, provided, however, that all money in said fund shall be kept on deposit in the county treasury or be invested in bonds or other securities authorized by the laws of the State of California as legal investments for savings banks. Such bonds or securities shall be placed in the custody of the county treasurer for safekeeping.