The Latest on six Illinois prison workers assaulted by inmates (all times local):

2:15 p.m.

An Illinois prison spokeswoman says an assault on six workers by five inmates at the maximum-security Pontiac Correctional Center appears to have resulted from a failure to follow workplace safety procedures.

Illinois Department of Corrections spokeswoman Nicole Wilson said Monday that the agency's investigation of the incident will include looking into why procedures weren't followed and how future incidents can be prevented.

Wilson says the assault doesn't appear to have resulted from a lack of policy or a breakdown in existing policies. She was responding to a union statement that policies and procedures designed to keep staff safe have been ignored or superseded by new practices.

The American Federation of State, County and Municipal Employees says the assault Sunday was sparked by an inmate punching a correctional lieutenant.

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11:50 a.m.

The union representing Illinois prison workers says an inmate punched a correctional lieutenant, sparking an assault that involved six prison employees and five inmates.

The American Federation of State, County and Municipal Employees said Monday that four correctional officers and two lieutenants at Pontiac Correctional Center were treated for abrasions, contusions and possible concussions suffered in the incident Sunday. They have all been released from the hospital.

The Illinois Department of Corrections has put the facility on lockdown and is investigating.

Joe Lewis is a correctional officer at the facility and president of the AFSCME local that represents the prison workers. He says an inmate started punching the lieutenant and knocked her to ground, then other inmates joined the fray, injuring other employees who tried to help the lieutenant.

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8 a.m.

A prison in central Illinois has been placed on lockdown while state officials investigate the assault of six employees by five inmates.

Illinois Department of Corrections spokeswoman Nicole Wilson said Monday that the Pontiac Correctional Center is on lockdown following the incident Sunday and will remain on lockdown until the department has finished its investigation.

She didn't say what a lockdown at the facility entails. The prison's website says no visitors are allowed.

The six employees who were assaulted have been treated for non-life threatening injuries and released from the hospital.

Wilson says the case will be referred to Livingston County prosecutors.

The prison is about 100 miles southwest of Chicago. It has maximum and medium security areas and can house nearly 2,300 inmates.

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7:35 a.m.

Illinois prisons officials say six employees who were assaulted by five inmates have been released from the hospital.

Illinois Department of Corrections spokeswoman Nicole Wilson said Monday that the staff members suffered non-life threatening injuries in the incident Sunday at Pontiac Correctional Center. Wilson said Sunday evening that the employees were hurt in an assault, but didn't offer details.

Wilson says the case will be referred to the Livingston County State's Attorney's office for prosecution when the department's investigation into the assaults is finished.

The prison is about 100 miles southwest of Chicago. It has maximum and medium security areas and can house nearly 2,300 inmates.