Illinois Department of Corrections records show that serious assaults at the Menard Correctional Center are up so far this year.
20 serious assaults were reported by May 29. That's an average of four a month. The prison in Chester had 30 assaults in all of 2012, an average of two and a half a month.
Three inmates have been killed this year at the maximum-security prison.
The American Federation of State, County and Municipal Employees represents guards in the state's prisons. Spokesman Kevin Hirsch says overcrowding and short staffing are in part to blame.
Corrections spokesman Tom Shaer says the department doesn't believe it can read much into five months of results.
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