CHICAGO (CBS) — A recent manager at the John Hancock Observatory and registered sex offender has pleaded not guilty to child pornography charges.

Christopher Colon pleaded not guilty to the three-count indictment Monday during an arraignment with U.S. Magistrate Judge Young Kim.

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Christopher B. Colon, 37, is a registered sex offender.

Not only did the convicted child sex offender occasionally work near children at the popular observatory, but he has also been under federal investigation for allegedly engaging in child porn since last fall, all raising questions about how he got the observatory job in the first place.

37-year-old Christopher Colon has been a registered sex offender in Illinois for three years, stemming back to a 2015 guilty plea.

As a result, a Cook County judge told the Northwest side man he couldn’t work at any job bringing him in direct contact with minor children without court approval; but that did not stop Colon from landing a job as Observatory Manager in the former Hancock Building.

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According to a federal search warrant application from April, Colon held that job while still on probation for the 2014 offense.  He continued to work there as Homeland Security agents began investigating him for allegedly seeking to engage in sexual exploitation and abuse of minors last fall. In some cases, the Feds allege he wanted some encounters to take place at 360 Chicago.

The 38-page affidavit states, among other allegations, that Colon used Craigslist to try to solicit fathers or uncles who would allow him to engage in sex acts with their sons or nephews. He offered private tours of the observatory to do so.

A 360 Chicago spokesperson, Natalie Stanichuk, says multiple background checks were conducted on Colon, but nothing negative came up. As a result, they’ve asked the search company, ADP, to review its background search process and report back on the failure to flag Colon.

Colon was flagged by the Feds last fall after they arrested a Wisconsin man for child pornography and found graphic exchanges between the two.

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Colon has not been charged in this ongoing investigation, but he is no longer working in the observatory.