Seven inmates were killed and at least 17 more were injured in seven hours of chaos at a maximum security prison holding some of the state's most unsafe convicts, authorities said Monday.
Of South Carolina's nine all-male, maximum-security prisons, Lee Correctional Institution is the largest.
The state's Corrections Department described the fights as "multiple inmate-on-inmate altercations".
He said no officers were wounded.
Lee Correctional Institution was secured at around 2:55 a.m. after incident involving inmates in three housing units, the South Carolina Department of Corrections wrote on Twitter. It is in Bishopville, S.C., about 40 miles east of Columbia, the capital.
Though most of the autopsies have yet to be performed, it appears that numerous prisoners died from stabbing or slashing wounds from "shanks", Lee County Coroner Larry Logan said.
They say the incident resulted in 17 inmates requiring outside medical attention and seven inmates were killed.