Michigan Compiled Laws, Chapter 38. Civil Service and Retirement § 38.2206

Sec. 206. (1) The state treasurer is the treasurer of the retirement system. The state treasurer has investment authority, including the custodianship of the funds of the retirement system, and has fiduciary responsibility with regard to the investment of funds of the retirement system. The state treasurer shall invest the funds of the retirement system in compliance with Act No. 314 of the Public Acts of 1965, being sections 38.1132 to 38.1140i of the Michigan Compiled Laws.

(2) The state treasurer shall deposit the funds of the retirement system in the same manner and subject to the laws governing the deposit of state funds by the state treasurer. The state treasurer shall credit income earned by the retirement system's reserves to the respective reserves under this act that earn the income as provided in section 213.  1