Inmates refusing to return to their cells assaulted nine staff members Wednesday evening at the Lincoln Correctional Center, the Nebraska Department of Corrections said.
All nine were taken to local hospitals -- six by ambulance and three by state vehicle -- said prisons spokeswoman Dawn-Renee Smith. All were expected to be released soon.
No inmates were hospitalized, and Smith said she was unaware whether any were injured.
Rescue workers first responded around 6:40 p.m. to the medium/maximum security prison, located at 3216 West Van Dorn St., after the inmates refused to return to their cells.
Smith didn't say how many inmates were involved or where the incident took place within the prison grounds. She said staff reacted quickly and contained the situation.
Several staff members were pepper-sprayed in the assault, according to 911 radio traffic.
Lincoln Correctional Center spokeswoman Tammy Kluver told reporters the prison would remain on lockdown overnight. State troopers blocked off the prison entrance for about two hours after the incident.
A spokesman for Gov. Pete Ricketts referred questions to the Corrections Department.
Wednesday's assaults came just three days after an inmate wrapped his arms around a staffer's neck at the same prison, causing injury. Earlier this month, staff there used pepper spray to subdue an inmate after he began punching a caseworker in the head.
The facility for adult males opened in August 1979. It was operating at 163.6 percent of its design capacity in June and has been without permanent leadership for more than two months.
Fred Britten was appointed interim warden after former Warden Mario Peart was reassigned, then retired following the June 10 escape of two convicted sex offenders.
Escapee Armon Dixon was recaptured a day later after physically assaulting two women at a central Lincoln apartment complex. Timothy Clausen was arrested in Omaha on June 15.
Wednesday's violence is the latest in a series of incidents at Nebraska prisons since a riot erupted at the Tecumseh State Correctional Institution in May 2015. The Mother's Day riot left two inmates dead and resulted in extensive reviews of safety and staffing within the state prison system.
Even then, Nebraska's correctional system was already under scrutiny because of prison overcrowding and hundreds of inmates who were released early because of mistakes in calculating their sentences.