Mich. Comp. Laws § 769.4: Conditional sentence; execution.

Sec. 4.

The person against whom any such conditional sentence shall be awarded, shall be forthwith committed to the custody of an officer in court or to the county jail, to be detained until the sentence be complied with; and if he shall not pay the fine within the time limited, the sheriff shall cause the other part of the sentence to be executed forthwith.