SPRINGFIELD - A ceiling at a Thomson Correctional Center minimum-security wing that normally holds about 40 inmates collapsed Monday. No one was hurt in the dormitory-style room where inmates sleep on bunk beds. And the roof itself remained intact, corrections officials said.

An inmate reported hearing a strange noise coming from the ceiling, and a prison guard evacuated everyone, a union official said. After that, the drywall ceiling, along with all the light fixtures, crashed to the ground.

"Most of it came down," said spokesman Derek Schnapp.

Now, corrections officials are inspecting the three similar minimum-security wings at Thomson to see if those ceilings too are prone to collapse.

Thomson holds about 160 minimum-security prisoners.

But, the prison's larger, maximum-security facility has gone mostly unused since it was built in 2001. Gov. Rod Blagojevich is in the process of trying to close Pontiac Correctional Center and move many of the inmates to Thomson's unused cells.

Pontiac-area officials and the state's largest employees union have opposed the move.

The minimum-security facility is separate from the maximum-security wings where Pontiac inmates would go.

Still, state Sen. Dan Rutherford, R-Chenoa, said the ceiling collapse raises more questions about whether Thomson is ready to go.

"This accelerated move just doesn't seem to be appropriate," Rutherford said. "This shows that there's problems."

Schnapp said he had no cost estimates to repair the ceiling problem.

Earlier this month, a review of state records showed last-minute upgrades to Thomson - including new fences, roofs and computer software needed to house Pontiac inmates - would cost about $424,000.