Suspicious Device at Liberty Bell? UPDATE: false alarm

CBS reporting a suspicious device is prompting evacuations near the site of the Liberty Bell. The device is described as containing a balloon and an unidentified white powder. Sounds weird to me, another false alarm?

ABC news adds this:

... a field test on the substance came back positive for some kind of biological agent. However, the field test is only a preliminary step, and more thorough tests on the substance are now being performed.

Update: Reuters quotes an FBI spokesman who contradicts ABC, stating the powder has "tested negative for radiological, biological and explosives".

UPDATE 2: Yep, another false alarm.