The union that represents Illinois prison guards says inmates at the Logan Correctional Center committed about 400 assaults since the lockup was converted to an all-women facility in 2013.
However, Corrections Department officials are disputing the numbers.
The American Federation of State, County and Municipal Employees released documents Thursday showing assaults ranging from spitting to fighting, kicking and punching.
The union obtained the unofficial report showing assaults on correctional officers, other staff and fellow prisoners. It says understaffing and overcrowding cause the problems.
Corrections Department spokesman Tom Shaer says the report AFSCME obtained includes incidents that were unintentional and not formally counted against the inmate. He says there were actually 273 inmate assaults during that time, and only four were serious.
The prison is located in Lincoln.
