LINCOLN, Neb. — Nebraska’s prison system faces renewed scrutiny following an attack that sent nine corrections employees to the hospital, the latest in a string of incidents that included a deadly riot and the escape of two convicted sex offenders.

Authorities said they have identified roughly a dozen inmates so far who were involved in Wednesday evening’s assault at the Lincoln Correctional Center, a medium-maximum security prison. The staff members were treated at hospitals and released.

State officials have approved millions in new funding over the last few years to address overcrowding and staffing shortages in the prison. But lawmakers said Thursday that they’re concerned about what appears to be an increase in violence from inmates, and Gov. Pete Ricketts canceled a scheduled town hall event so he could meet with prison employees and the department’s director.

“It appears to me that it’s escalating,” said Sen. Les Seiler, chairman of a special prisons oversight committee. “I don’t know if there’s a silver bullet. I think you have to look at the overall picture, at the lack of programming, treatment and staff.”

Seiler said lawmakers may have to take more action in next year’s session, “and I would assume it’s not going to be cheap.” The prisons committee is scheduled to meet next week to hear testimony on staffing shortages.

Nebraska’s corrections department has faced a series of dangerous, high-profile incidents in the last 15 months. Two inmates died in a May 2015 riot at the Tecumseh State Correctional Institution in southeast Nebraska, and in June, two convicted sex offenders escaped from the same prison where Wednesday’s attack occurred. They were caught days later, but one is accused of attacking two women in a Lincoln apartment.

The prison’s warden retired shortly after the escape, and no permanent replacement has been found.

Lincoln Correctional Center spokeswoman Tammy Kluver said investigators are trying to determine exactly what happened Wednesday. The Nebraska State Patrol is reviewing video footage of the incident, which took place around 6 p.m. in a small courtyard outside of the facility’s housing units.

In a statement, the Department of Correctional Services said the incident began when one inmate struck a staff member, which led to other inmates assaulting employees in the area. Kluver said the inmates involved refused to return to their cells, and authorities used pepper spray to subdue them. One female staffer needed staples to close a gash in her head, while others suffered cuts and scrapes.

The prison, which houses men, was still on lockdown Thursday.

Correctional Services Director Scott Frakes said his agency is doing everything it can to prevent violence against staff members. Frakes said prison crowding and staffing levels had nothing to do with the attack; the Lincoln Correctional Center was considered fully staffed when it occurred.

“Inmates made the choice to harm staff,” he said.

Sen. Colby Coash of Lincoln, whose district includes the Lincoln Correctional Center, said many of his constituents who work at the prison are suffering from fatigue because of mandatory overtime and high turnover rates that force them to shoulder a larger workload in a stressful environment. Many seasoned employees have left because the state no longer offers longevity pay.

“They need to be listened to,” Coash said. “Their morale is poor, their safety is at risk, and they’re not being given the tools they need. We need to start recognizing the value of what these people do every day.”