FORT MADISON, Iowa (AP) — Iowa prison officials say inmates assaulted three staff members on duty at the Iowa State Penitentiary in Fort Madison.

The Iowa Department of Corrections says in a news release that the assault occurred Thursday morning. Officials say a preliminary investigation shows two inmates assaulted another inmate with several sharpened objects. Correctional officers responded, and three suffered minor injuries in the course of subduing the attacking inmates. Officials say it did not appear that the officers were cut by the attackers.

Two of the officers were taken to a local hospital. The third was seen by institution medical personnel and returned to work.

The inmate attack also was taken to a hospital. Officials say his wounds appear not to be life-threatening.

Visits to the prison have been suspended until further notice.