"What we believe from initial investigation is that this was all about territory, about contraband, about cellphones," said Bryan Stirling
, the state's director of corrections.
"These folks are fighting over real money and real territory while they're incarcerated."
The first melee started around 7:15 p.m. Sunday in a dorm housing about 250 inmates. Response teams from across the state started heading toward the facility in Bishopville, Stirling said.
Around 8:30 p.m., more fracas erupted in two other dorms, Stirling said.
By 11:30 p.m., "We entered the first dorm at Lee to take that dorm back," Stirling said. "We had enough people there to enter safely, and we took that dorm back."
By 2 a.m. Monday, all dorms had been secured.
But in the hours of ruckus, seven inmates
-- Raymond Angelo Scott, Michael Milledge, Damonte Marquez Rivera, Eddie Casey Jay Gaskins, Joshua Svwin Jenkins, Corey Scott and Cornelius Quantral McClary -- were killed.
Another 17 inmates were injured, the department of corrections said. No officers were hurt.
South Carolina officials have asked the Federal Communications Commission to allow them to block cellphone signals in prisons and have a meeting with the FCC in May to discuss the issue.
"Through these contraband cellphones that the FCC will not allow us to block, they're able to conduct their criminal enterprises," Gov. Henry McMaster said.
"It's not a South Carolina problem," Stirling said. "It's a national problem."
4 deadly incidents in 1 year
Lee Correctional Institution, a maximum-security prison for men
, has been the site of several other violent and deadly outbreaks this past year, CNN affiliate WACH
Last month, inmates reportedly overpowered an officer for more than an hour
and took control of one side of a housing unit.
In February, inmate Robert Odell Brown was killed by another inmate
at Lee Correctional Institution.
Last November, another dispute between two prisoners led to the stabbing death
of inmate Larry Rainey.