SPRINGFIELD, IL - State officials tightened security at two prisons this month after inmate fights, and the prison officers' union is blaming the problems on dangerous understaffing.

A correctional officer was injured Tuesday night when intervening in a fight between two inmates at Centralia Correctional Center, prison spokesman Derek Schnapp said. According to the American Federation of State, County and Municipal Employees, the officer suffered a broken leg.

Centralia was locked down - which generally restricts inmates to their cells - until Thursday morning, Schnapp said.

Lawrenceville Correctional Center in southeastern Illinois has been on lockdown since June 30 after several inmates fought, Schnapp said. An investigation into the incident continues there. No charges have been filed in either case.

About 2,500 AFSCME members picketed prisons statewide June 20 to protest what the union says is understaffing. The union claims understaffing has contributed to three violent incidents in the past four months, including the sexual assault of two employees and an inmate's murder.

Schnapp said the problems are unrelated to the number of COs.

The state budget includes money for 250 new officers, but AFSCME says the system needs 600 on top of that - at a cost of $24 million - to help keep prisons safe.

"The time even for dialogue is in the past," AFSCME spokesman Anders Lindall said. "This problem will only be resolved by immediately adding additional security staff."