Chicago police are investigating cases of suspicious activity at two Loop buildings. One of them is the Sears Tower.Related Links

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Since 9-11, the Sears Tower in particular has turned up on several lists of possible targets for terrorists. ABC7 news has reported sightings of suspicious looking individuals photographing the building numerous times in the past several years. Law enforcement officials have always publicly downplayed these incidents and they attempted to do that again Thursday.

Sears Tower employees Thursday reportedly received bulletins from building management reassuring them that there is no terror threat. But those bulletins failed to explain the incident ABC7 reported, that three suspicious looking men in a rental car pulled up to the building recently, got out and began studying the building. According to law enforcement sources, they took pictures before building security ran them off, but they never got their identification. Those sources tell ABC7 the car was rented to a fake name.

The entire incident was captured on building security video, which was turned over to members of the Joint Terrorism Task Force.

A Sears Tower spokesman said Thursday the men were not taking pictures. He issued a statement saying “investigators later reported back to Sears Tower security that they had no reason to believe the activity was criminal or cause for any further concern.”

Law enforcement sources however have told ABC7 news the investigation is ongoing and they have been unable to identify the men from the video.

Sources also say a second suspicious incident at the Boeing corporate offices is also under investigation. This time a lone man, reportedly suspicious looking, was seen sketching the building. Security questioned him and took pictures of his sketch, though they never got his ID. A Boeing spokesman Thursday confirmed they reported it to authorities who have been conducting an investigation.

FBI spokesman Ross Rice says the Sears Tower incident actually happened several months ago. He contradicts the information from our sources. Ross said investigators were able to trace the car outside the Sears Tower to a real person who they determined was not a threat.

But this incident is just the latest of a number of similar ones we have reported on over the last few years.