COLUMBIA, S.C. (AP)- An inmate who witnessed a riot inside a South Carolina prison says he saw bodies stacking up on each other and correctional officers didn't do anything to stop the violence or check on the injured.

A spokesman for the state's prisons says seven inmates were killed and at least 17 others were seriously injured as inmates fought uninterrupted for more than seven hours. Officials didn't immediately say what sparked the violence.

No prison guards were hurt.

The prisoner who saw the riot exchanged messages with AP on the condition of anonymity because he is not allowed to have a cellphone and fears retribution from other inmates. He says most of the inmates are affiliated with gangs and several attackers taunted a rival gang member who was hurt.