Shortly before 10 a.m. Friday, the doors on a 16-cell housing gallery at the Tecumseh State Correctional Institution were opened in error.
The doors are operated by a computerized system, spokeswoman Dawn-Renee Smith said. The cause of the error is under investigation.
The inmates were in their cells and were directed to remain inside, but came out into the gallery and refused to return to their cells.
Dawn-Renee Smith said no staff members were on the gallery at the time the doors opened.
While the inmates comingled, one inmate was assaulted by one or more of the others and seriously injured. Another inmate sustained non-serious injuries, the cause of which has not been determined.
The injured inmate was removed from the gallery and received medical treatment, Dawn-Renee Smith said.
Detention officers used uspecified chemical agents to clear the gallery and return the inmates to their cells, but inmates continued to resist, starting a fire in one of the cells. The Tecumseh Volunteer Fire Department responded. The fire was contained to one cell. The State Fire Marshal was notified.
The corrections emergency response team was activated and prepared to enter the gallery; however, the incident was resolved before that was necessary, with inmates complying with directives.
No staff members were injured. One staff member sought medical attention for possible smoke exposure.
All inmates on the affected gallery were accounted for.
The remainder of the facility was not involved, but went to modified operations as a precaution.
The Nebraska State Patrol investigated the incident and assaults.