Liberty Bell Evacuation: Could Food Network be at Fault for White Powder?

PHILADELPHIA (CBS/AP) Police are investigating the source of a powder-filled balloon that forced the evacuation of the Liberty Bell Center in Philadelphia for a few hours Thursday.

Spokesman Lt. Frank Vanore said Friday that city police questioned whether it was linked to the taping of a TV program.

But a Food Network statement says no balloons were used in the network's Thursday morning taping of  "Chef vs. City."

A guard discovered the stray balloon outside the Liberty Bell entrance that afternoon, leading authorities to shut down the area. The FBI says tests show the powder was not hazardous, but more tests were planned. The National Park Service says the substance was flour.

Meanwhile, police say powder found on a letter to a municipal office building near Philadelphia City Hall that also prompted a limited evacuation Friday,  also was not hazardous.