No police officers or jail employees were injured, the section mentioned.
Deadly prison riots have been relatively rare in the United States, despite some notable exceptions.
The South Carolina Department of Corrections says the incident started at 7:15 p.m. on Sunday and it involved multiple inmate on inmate altercations in three housing units. He said 17 inmates required medical attention outside the prison.
SC state police have been called to an "ongoing situation" at one of the state's most unsafe prisons.
Lee County Coroner Larry Logan told The Associated Press that he arrived to a chaotic scene of fights everywhere at Lee Correctional Institution.
South Carolina Department of Corrections did not immediately return a request for comment Monday morning.
Logan said he just finished identifying all the dead Monday and is working to notify relatives.
Lee County Fire/Rescue said ambulances from at least seven jurisdictions lined up outside the prison to tend to the wounded.
In February, an inmate was killed by another inmate in a fight.
In March, inmates at the prison held an officer hostage after taking control of a dorm room, The State reported.
IMD predicts normal monsoon this year
A normal monsoon will not only aid agriculture growth but could have a positive impact on the overall rural economy. The monsoon is considered normal if the average rainfall is between 96 to 104 per cent of long period average.