An incident at a South Carolina prison has left seven inmates dead and 17 others injured.

WIS reported that there were multiple inmate-on-inmate fights at the Lee County Correctional Institution Sunday night.

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The prison was secured around 2:55 a.m., more than seven hours after the altercations started.

No prison staff or law enforcement officers were injured in the incident, WIS reported.

The state's Department of Corrections and the S.C. Law Enforcement Division are both investigating, WSPA reported.

The prison is a Level 3 facility, which holds "violent offenders with longer sentences, and inmates who exhibit behavioral problems," WPDE reported. "Inmates at level 3 facilities are closely supervised and their activities and movement within the institution are highly restricted."

Two corrections officers were killed in a 2015 fight. An inmate killed another in February, The Associated Press reported.