In September, American intelligence officials intercepted some innocuous-looking packages being shipped to Chicago from Yemen. The boxes were filled with religious books and papers.
Acting on a tip that the packages were sent from someone connected to al-Qaida's arm in Yemen -- al-Qaida in the Arabian Peninsula (AQAP), U.S. officials opened the packages. They didn't find explosives or anything remotely suspicious, so they allowed the boxes to continue on to Chicago. The episode was filed away as a strange occurrence -- until last week.
Some intelligence officials now wonder if that episode may have been part of a dry run ahead of last week's package bomb scare. If so, that would have allowed the senders to obtain information on how a package makes its way from the Middle East to the U.S.
But now intelligence officials tell NPR they are looking at a broader, more troubling question: What if last week's bomb-laden packages were also a trial run –- an effort to see if security could detect explosives if they were sent in boxes to the U.S.?
"If that's what it was, if it was a trial run to see how we'd respond to well-hidden explosives, then we failed -- big time," said one intelligence official.
The two packages discovered last week contained Hewlett-Packard computer printers and clothes and books. The boxes -- one found in East Midlands Airport in the United Kingdom and one found in Dubai -- looked like the kind of packages a student might send home at the end of the semester. And, in both cases, the powdered ink inside the printer cartridge had been replaced with PETN, a powerful explosive related to nitroglycerin that has been the explosive of choice for AQAP. And officials almost missed it.
When U.S. authorities called their counterparts in Britain, they provided the precise tracking number of the package being sought. Officials at East Midlands Airport located the box, scanned it, had bomb-detecting dogs sniff it and assured authorities in Washington that there were no explosives found. That's one of the reasons why for much of the day on Friday news outlets were reporting that the box found in the United Kingdom was harmless.
U.S. authorities insisted officials at East Midlands check the package again. It was only on this second round, when they opened up the printer box and looked at the toner cartridge inside the printer that they realized it did indeed contain explosives –- and hidden underneath was a circuit board wired up to detonate it.
If the two boxes sent last week were a test, then whoever was behind them has learned, quite publicly, that the scanning machines they are using in the United Kingdom don't detect PETN and -- this is well-known -- that bomb-detecting dogs are, at best, unreliable.
Officials were able to get some clarity on another episode that looked suspiciously like it was connected to this latest plot. On Sept. 3, a UPS cargo plane went down near Dubai. NTSB officials said at the time there was an onboard fire.
The Obama administration's top terrorism official, John Brennan, said over the weekend that the U.S. was taking another look at the cause of that crash.
The flight recorders from that plane were brought to Washington and re-examined. Two officials familiar with this second investigation told NPR that investigators couldn't find a "pressure signature" on the flight recorder, which would have been the sign of an explosion on board. There also wasn't the sound of an explosion on the voice recorder.
Officials are standing by their original conclusions that the early September crash was a tragic accident, not a terrorist plot. There could be a formal announcement of their findings this week.