LINCOLN, Neb. (AP) — State officials say an inmate has injured three staffers at the Nebraska State Penitentiary in Lincoln.

The Nebraska Department of Correctional Services says the inmate began punching a guard around 2 p.m. Tuesday and then struck two other staff members who went to the guard’s aid. The department says the guard was taken to a hospital for treatment of non-life-threatening injuries and says the two other staffers sought outside medical treatment.

The department says the facility’s medium/maximum-security housing units soon were locked down, restricting movement for about half the prison population.

The department says it will investigate the incident and forward results to the Lancaster County attorney for a decision on any prosecution. The names of those involved haven’t been released.