After a deadly riot at a South Carolina prison on Sunday, state prison officials said cell phone use was to blame for the violence.

Department of Corrections Director Bryan Stirling said in a press conference on Monday that a fight that left seven inmates dead and 17 inmates injured at Lee Correctional Institution in Bishopville was about territory, cell phones, and contraband. “These folks are fighting over real money,” he said.

Both Stirling and South Carolina Gov. Henry McMaster said that stopping cell phone signal access in prison could lessen prison violence. Cell phone usage at Lee Correctional is illegal, but Stirling said prisoners use cell phones to engage in criminal activity. The Federal Communications Commission currently outlaws cell phone jamming, or blocking access to signals.

A prisoner who witnessed the riot told the AP the incident was gang-related.The correctional officers did not intervene in the disturbance, according to the prisoner: "It's been over two hours, but no COs (corrections officers) have responded to this unit, and no medical personnel have attempted to render any kind of aid.”

State prison officials said in a statement that no correctional officers were injured during the altercation that happened across three wards, according to state prison officials.

Fights broke out in the prison around 7:15 a.m. Sunday night, according to state prison officials, and it took officers nearly 8 hours to contain the riot. South Carolina prison guards are unarmed, according to the AP.

The names of the inmates killed were released Monday morning by the South Carolina Department of Corrections: Raymond Angelo Scott, Michael Milledge, Damonte Marquez Rivera, Eddie Casey Jay Gaskins, Joshua Svwin Jenkins, Corey Scott, and Cornelius Quantral McClary.

Lee Correctional has a history of violence, according to a Charleston Post and Courier recap of violent incidents at prisons throughout the state. In 2010, an inmate called a hit on a prison official who was shot six times at his home. In 2012, correction officers were held hostage by prisoners on two separate occasions. In 2016 and 2017, inmates were stabbed to death at Lee. Just last month, a prison guard suffered injuries after was held hostage by inmates for over an hour before surrendering.

In South Carolina, 12 inmates were killed by fellow prisoners in 2017, compared to 5 inmate-on-inmate deaths in 2016. Two inmates were killed by other prisoners at Lee Correctional last year. The worst South Carolina prison killing last year was at Kirkland Correctional Institution in Columbia, where four inmates were strangled to death by fellow prisoners at an unsupervised mental health wards for being ‘nuisances,” The State reported.

SCDC head Stirling told The State the statistics were not surprising and pointed to the widespread use of cellphones as a reason for prison violence. He also noted that state prisons are understaffed.

Lee Correctional opened in 1993 and houses 1,266 inmates, according to the prison’s website. Only 44 officers were on staff during Sunday evening’s prison riot, according to Stirling.

When asked what SCDC officials would say to the dead inmates’ family and friends, Stirling said, “We did everything we could in our power to get there as quickly as possible.”