Mich. Comp. Laws § 38.1140b

Sec. 20b. An investment fiduciary may make interest bearing deposits with the treasurer of the political subdivision sponsoring the system or with the state treasurer, either of whom may then manage and invest the deposits in a collective investment fund, common trust fund, or pooled fund that is established and maintained for investment of those assets by the treasurer of the political subdivision sponsoring the system or by the state treasurer in accordance with this act.