At least seven inmates died and 17 others were injured during eight hours of rioting at a maximum-security prison in South Carolina on Sunday and Monday, a lengthy series of clashes that authorities said gained fuel because of contraband cellphones inmates carried within the facility.

State officials defended their response to the prison brawl — one of the deadliest in the country’s recent history — amid questions about the extent of the injuries and fatalities and how long the violence lasted.

Fighting began at about 7:15 p.m. Sunday at one of the housing units at Lee Correctional Institution, in Bishopville, about 60 miles northeast of Columbia. Detention officers had been conducting a nightly check-in when the confrontations started, state Corrections Director Bryan Stirling said at a news conference Monday. Two more fights broke out at about 8:30 p.m. at two other housing units at the prison.

Stirling said it is unclear exactly what prompted the riots but said that officials believe word of the fights spread from the first dorm to the others through contraband cellphones.

“This was all about territory. This was about contraband. This was about cellphones,” Stirling said. “These folks are fighting over real money and real territory when they are incarcerated.”

The Corrections Department identified the seven dead inmates as Raymond Angelo Scott, Michael Milledge, Damonte Marquez Rivera, Eddie Casey Jay Gaskins, Joshua Svwin Jenkins, Corey Scott and Cornelius Quantral McClary.

It was unclear what roles the deceased played in the fights. Thom Berry, a spokesman for the South Carolina Law Enforcement Division, said an investigation is underway “to determine what caused the disturbance.”

The fighting triggered a standard response from prison guards: Guards at each of the dorms left the housing units and called for backup, Stirling said.

“They’re outnumbered, so they’re trained to back out of that dorm and call for support,” Stirling said. “And that’s what we believe they did last night because support arrived immediately.”

Backup teams from SLED entered the first housing unit at 11:30 p.m. Sunday to “take that dorm back.” They did the same for the second and third dorms at 12:30 a.m. and 2 a.m. Monday, he said. The prison was secured at 2:55 a.m. Monday, and no officers or staff members were harmed, officials said.

Emergency crews from at least a half-dozen agencies responded to the “mass casualty incident,” according to Lee County Fire and Rescue. The Lee County coroner told the Associated Press that most of the dead appeared to have been killed by stabbing or slashing with improvised knives.

Lee Correctional Institution is one of South Carolina’s highest-security prisons; inmates generally are under tight monitoring and their movements inside the facility are limited.

Of South Carolina’s nine all-male, maximum-security prisons, Lee Correctional is the largest. The prison houses about 1,600 male inmates, the majority of them in general housing, according to state records.

Violence at Lee Correctional is not uncommon. During the past year, at least three inmates were killed there in separate incidents, while last month, inmates held an officer hostage for about an hour and a half before releasing him, according to the State newspaper.

An investigation by the State’s John Monk found that the number of inmates killed across the state’s prisons rose from three inmates in 2015 to 12 inmates in 2017. Stirling told Monk that the trend can be attributed in part to an increase in inmates obtaining cellphones, chronic understaffing, gang rivalries and a higher ratio of violent prisoners to nonviolent ones.

On Monday, Stirling said the corrections department would continue to push the Federal Communications Commission and cell service providers to block cellphone signals at the prison.

“Until that’s done, the folks that are incarcerated are going to continue their criminal activity, which is not only dangerous on the inside, but it’s also dangerous on the outside,” he said.

Gov. Henry McMaster (R) expressed confidence in Stirling as the head of the Department of Corrections and said at a news conference that the riot was an unfortunate but unsurprising incident. He said inmates “take their violent ways with them” when incarcerated.

“We know that prisons are places where people who have misbehaved on the outside go for rehabilitation and also to take them from the general population,” McMaster said. “It’s not a surprise when we have violent events take place inside the prison, any prison in the country. … It is unfortunate when they do happen, but this is one of those instances when they did.”

According to the department, the number of inmates held in state prisons has declined in recent years after peaking nearly a decade ago. More than 20,400 inmates were incarcerated in South Carolina facilities last year, down from a peak of 24,040 in 2010, state records show.

This post has been updated.

Read more: