The funds of the retirement system shall be invested under the general direction of the retirement committee. The city or the retirement committee if delegated such function by the city shall select and contract with a funding agent or agents to hold or invest the assets of the retirement system and to provide for the benefits provided by the Police Officers Retirement Act. The city or committee may select and contract with investment managers registered under the federal Investment Advisers Act of 1940 to invest, reinvest, and otherwise manage such portion of the assets of the retirement system as may be assigned by the city or committee. All funds of the retirement system shall be invested pursuant to the policies established by the Nebraska Investment Council.