Eleven inmates at the South Dakota state prison have all pleaded not guilty to a combined 18 felony charges stemming from the March 27-28 disturbances at the State Penitentiary in Sioux Falls.

The inmates entered their not guilty pleas during an arraignment Wednesday in Minnehaha Circuit Court.

Inmates face charges including aggravated assault, simple assault, damage to prison property, and starting fires within the prison. All inmates also face habitual offender charges.

On of the inmates, 45-year-old Joshua D. Vortherms, faces two counts of Aggravated Assault Against a Department of Corrections employee and two counts of Simple Assault Against a Department of Corrections employee.