Texas Department of Criminal Justice spokesman Jason Clark says 55-year-old Mari Johnson was found unresponsive about 3 a.m. Saturday near the kitchen area of the Robertson Unit.
He says life-saving measures were initiated and Johnson then was taken to Hendricks Medical Center in Abilene where she was pronounced dead. Johnson had been with the prison system since August 2009.
Clark says the agency's Office of Inspector General is investigating and no additional details are being released.
The Robertson Unit has a capacity of nearly 3,000 inmates.
"We will see that the offender who committed this cowardly act is held accountable," said Brad Livingston, Executive Director of the Texas Department of Criminal Justice, according to NBC News.
"Correctional officers have one of the most difficult jobs in all of state government, protecting the public from dangerous individuals," Livingston said. "This is a tragic reminder that carrying out that mission can lead to the ultimate sacrifice. Ms. Johnson made the ultimate sacrifice to keep this state safe." Johnson was a seven-year veteran of the criminal justice department.
It's been a year since the last Texas corrections officer was killed on the job, at the Telford Unit near Texarkana.