PHILADELPHIA (AP) -- Investigators are trying to identify a white powder found inside a balloon at the downtown Philadelphia building that houses the Liberty Bell.
The Liberty Bell Center and part of a street next to it have been evacuated.
A guard found the balloon inside the visitors entrance to the Liberty Bell Center on Thursday afternoon.
FBI spokesman J.J. Klaver says testing is being done on the substance. He says it's not explosive or radioactive but is what he calls a "biological substance."
Klaver says one type of biological substance is anthrax, an infectious disease. But he stresses investigators don't know what the substance is.
Some nearby streets have been closed to pedestrians as the investigation continues. Vehicles can pass.
No injuries are reported.
(Copyright 2010 by The Associated Press. All Rights Reserved.)
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