A spokesman for its owner of the 83-story building, New York City-based Blackstone Real Estate Advisors, confirms the building is on the market, with Secured Capital Corp. brokering the sale. Officials of the New York City-based brokerage did not return telephone calls.

Meanwhile, a spokeswoman for Jones Lang LaSalle declined to confirm or deny reports her company is handling the sales effort for Prudential Plaza, located immediately west of Aon Center, for San Francisco-based Shorenstein Co., LP. The package includes 41-story, 1.76-million-sf One Prudential Plaza at 130 E. Randolph St. and 64-story, 1.4-million-sf Two Prudential Plaza at 180 N. Stetson Ave.

Blackstone paid $431 million for Aon Center in December 1998, financing the purchase with a $335-million mortgage. Shorenstein paid $372.6 million for Prudential Plaza in June 2000,with Fleet National Bank financing the sale with a $240-million mortgage. The sale raises eyebrows for reasons beyond the somewhat short holding periods.