YPSILANTI, Mich. (AP) — Officials say they're not sure what's causing an itchy rash affecting more than 100 inmates at Michigan's only prison for women.

The Ann Arbor News reports an estimated 115 inmates at the Huron Valley prison near Ypsilanti are believed to have the rash. The prison has about 2,100 inmates and the number affected is up from about 50 when the Detroit Free Press initially reported about the rash in March.

Department of Corrections spokesman Chris Gautz says the rash isn't believed to be contagious and the department is taking steps to try to stop it.

The rash has been described by inmates as bright red pimple-like bumps with occasional pockets of pus.

The prison has been subject to complaints and lawsuits by prisoners and guards about conditions at the facility.