CHICAGO (CBS) — An office building on Wacker Drive has been evacuated, and at least six people have been taken to hospitals, due to an apparent chlorine leak.

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The Fire Department first responded to the leak at 77 W. Wacker Dr. around 10 a.m., and the building later was evacuated. The hazardous materials response was secured shortly after 11 a.m., and people were being allowed back inside.

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Five people were taken to Northwestern Memorial Hospital and one was taken to Rush University Medical Center with injuries that were not considered life-threatening, according to police and fire officials.

Police confirmed the incident was the result of a chemical spill on the roof.

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Wacker Drive was closed in both directions between Dearborn and Clark during the hazmat response.