How far can MDCR investigation go?

Q. Our company is responding to a charge filed with the Michigan Department of Civil Rights (MDCR). The allegation relates to management’s treatment of one employee. However, during the investigation, the MDCR  asked us to produce various unrelated records—for example, promotion records. The charging party has made no claim that he was discriminated against with respect to any promotion. He has never even sought a promotion. How should we respond to this request? ...