Seven inmates were killed and at least 17 others were seriously injured after fights broke out between prisoners inside a maximum security prison in South Carolina.

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

Taillon said no officers were wounded after multiple inmate fights broke out at 7.15pm Sunday. He said 17 of the injured required medical attention outside the prison.

The South Carolina Department of Corrections tweeted that it involved multiple inmate on inmate altercations in three housing units.

Lee County fire/rescue said ambulances from multiple jurisdictions lined up outside the prison to tend to the wounded. The local coroner’s office also responded.

The maximum-security facility in Bishopville houses about 1,500 inmates, some of South Carolina’s most violent and longest-serving offenders.

These deaths at Lee are the most in any South Carolina prison in recent years. Four inmates were killed by a pair of prisoners in the state’s Kirkland Correctional Institution last year. Two officers were stabbed in a 2015 fight.