IRMA, Wis. — Authorities are investigating an assault at Lincoln Hills juvenile prison that sent one staff member to the hospital.

The Lincoln County Sheriff’s Office says an inmate assaulted the staff member Wednesday. The extent and nature of injuries are unknown. The names of the student and employee were not immediately released.

There has been unrest at Lincoln Hills and Copper Lake schools amid reports of inmate mistreatment and authorities have been probing allegations of prisoner abuse. No one has been charged but some top officials have resigned.

In July, a federal judge in Madison ordered the prison to reduce use of solitary confinement, pepper spray and shackles. This week, Gov. Scott Walker’s administration said it has made progress, but couldn’t immediately comply due to “significant unrest” at the facilities.