An anti-crime group in suburban Chicago has offered a $1,000 reward for the return of a concrete piece of the Pentagon that was stolen from a September 11 memorial.

Last week's theft was the second time in three years that rubble from the Pentagon has been stolen from the Naperville memorial. After the 2005 theft, city leaders installed a surveillance camera, which they said wasn't functioning during Wednesday's incident.

Police reports say the thief took the concrete piece after breaking a protective, heavy-duty plastic seal. A security guard discovered the damage.

The Naperville memorial honors victims of the terrorist attacks including Naperville native Navy Commander Dan Shanower, who died at the Pentagon.