At least some of the devices found in the
wave of suspected pipe bombs mailed to prominent political and media figures had no possibility of exploding — because they contained flaws in the way they were made, several investigators told NBC News on Thursday, based on early analysis.
In a few cases, the flaws were substantial, the investigators said. In others, the defects were more subtle. But there's still no way to know at this point whether the deficiencies were intentional — to make convincing hoaxes — or simply the result of bad design or construction, the sources said.