COLUMBIA, S.C. — A South Carolina prisons spokesman says seven inmates are dead and 17 others required outside medical attention after seven hours of fighting inside a maximum security prison.

Prisons spokesman Jeff Taillon announced the grim outcome after State Law Enforcement Division agents helped secure Lee Correctional Institution around 3 a.m. Monday.

Raymond Scott, Michael Milledge, Damonte Rivera, Eddie Gaskins, Joshua Jenkins, Corey Scott and Cornelius McClary were the seven inmates killed. Authorities said the majority of these men were stabbed or slashed. The others were beaten to death as multiple inmate-on-inmate fights broke out in three separate housing units, CBS News reported.

It’s still unclear what sparked the violence.

No officers were injured in the fight.

The maximum-security facility in Bishopville houses about 1,500 inmates, some of South Carolina’s most violent and longest-serving offenders. Two officers were stabbed in a 2015 fight. One inmate killed another in February.