Seven prison inmates were killed and 17 others were injured in an hours-long series of fights between inmates at a prison in South Carolina, the state Corrections Department said on Twitter on Monday.

The Lee Correctional Institution in Bishopville, South Carolina, about 40 miles (64 km) northeast of the state capital of Columbia, was secured at 2:55 a.m. EDT (0655 GMT), officials said. The violence began at around 7:15 p.m. EST (2315 GMT) on Sunday night, spilling out over three housing units.

All prison staff and law enforcement officers were safe and accounted for, officials said on Twitter. The prison has 1,583 inmates, according to its website.

It was one of the deadliest U.S. prison incidents in years. In 1993, nine inmates and one corrections officer died at the Southern Ohio Correctional Facility in Lucasville, according to local media.

One inmate died and eight were wounded in a September 2017 riot at a state penitentiary in San Luis Obispo, California. (Reporting by Rich McKay in Atlanta and Ian Simpson in Washington Writing by Scott Malone Editing by Chizu Nomiyama and Jeffrey Benkoe)