PHILADELPHIA -- There is no evidence that a bomb found in a Postal Service mailbox was related to Middle Eastern terrorists, despite a note on the parcel that read "Free Palestine now," authorities said Tuesday.
"No terrorist group has owned up to it. There is no indication at this point that it was terrorist related," said John Sinnen, assistant special agent in charge of the U.S. Postal Inspection Service in Philadelphia.
The device, which contained a foam box packed with nails and an explosive charge, was detonated Monday when a police bomb squad shot the package with a water cannon. The blast hurled shrapnel 100 feet, but injured no one.
The bomber's intended target was not immediately clear, authorities said.
Investigators described the device as more sophisticated than the series of crude pipe bombs that injured six people in the Midwest earlier this month.
The package carrying the bomb, found by a letter carrier in a Philadelphia mail drop, was not addressed and bore no postage. In addition to the note, which also mentioned the al-Qaida terrorist network, the parcel had protruding wires, Sinnen said.
The note and wires instantly caught the attention of letter carrier Matthew Widmeier, who found the package and immediately phoned authorities.
On Tuesday, the bomb squad was called after someone placed a pair of sneakers inside a mailbox outside a synagogue, along with a note that also mentioned Palestine.
It was found 2 1/2 miles from the box where Monday's bomb was discovered; both boxes are served by carriers from the Fox Chase Station post office.
Police don't yet know whether the two incidents were related.
Sinnen said investigators didn't have a suspect but were exploring several theories.