The State Treasurer shall be the custodian of the funds and securities of the retirement system and may deposit the funds and securities in any financial institution approved by the Nebraska Investment Council. The State Treasurer shall transmit monthly to the board a detailed statement showing all credits to and disbursements from the State Patrol Retirement Fund. The State Treasurer shall disburse money from such fund only on warrants issued by the Director of Administrative Services upon vouchers signed by a person authorized by the retirement board.