Officials said a prison for illegal immigrants in Mississippi remains on lockdown after a riot that began on Sunday left one guard dead and at least 19 people injured.

Mike Machak, a prison spokesman, said in a statement Monday that all inmates were secured in their housing units by 2:45 a.m. Monday, nearly 12 hours after the disturbance began at the Adams County Correctional Center in southwest Mississippi.

Officials haven't released the identity of the slain guard.

Machak said 16 other employees were treated and released from a hospital for various injuries. Three inmates were injured.

The prison is owned and operated by Corrections Corp. of America and holds illegal immigrants, most for charges of re-entering the United States after being deported.