Paris explosives are a key clue to plot

Story highlights

  • Peter Bergen: Terrorists used an unstable compound made from household ingredients
  • He says authorities in the United States and other Western countries need to be on the lookout for bulk purchases

Peter Bergen is CNN's national security analyst, a vice president at New America and a professor of practice at Arizona State University. He is the author of "Manhunt: The Ten-Year Search for bin Laden -- From 9/11 to Abbottabad."

(CNN)French prosecutors say the bombs used in the terrorist attacks in Paris on Friday were made from TATP, a fact that yields important clues about the way the plot was planned and executed.

TATP-based bombs are built using the common household ingredient hydrogen peroxide, which is used to bleach hair. Such bombs have been a signature of jihadist terrorists in the West for more than a decade because the materials are so easy to acquire, unlike military-grade explosives, which are tightly controlled in much of the West.
Their use in the Paris attacks, as well as in terrorist plots in London and in the United States over the past decade, should remind law enforcement in the West that these TATP bombs are what jihadist terrorists may deploy in the future.
    What is tricky about TATP bombs is that they are quite difficult to make because their ingredients, when combined, are highly unstable and can explode easily if mishandled. To make an effective TATP bomb requires real training, which suggests a relatively skilled bomb-maker was involved in the Paris plot, since the terrorists detonated several bombs.
    It also suggests that there was some kind of bomb factory that, as yet, appears to be undiscovered, because putting together such bombs requires some kind of dedicated space. And it also suggests that there were probably tests of the bombs in an isolated place to ensure that they worked.
    The dangers of TATP bombs can be seen in the case of Matthew Rugo and Curtis Jetton, 21-year-old roommates in Texas City, Texas. They didn't have any bomb-making training and were manufacturing explosives in 2006 from concentrated bleach when their concoction blew up, killing Rugo and injuring Jetton. The pair had no political motives: They had just wanted to blow up vehicles for fun.
    Others in the United States have built TATP bombs with far more malevolent intent. Najibullah Zazi, who grew up in New York City, wanted to blow up as many commuters as possible on the Manhattan subway system.
    Zazi was trained by al Qaeda to make a TATP bomb in Pakistan, and during the summer of 2009, he made bulk purchases of hair bleach in suburban Denver and set up his bomb factory in a nearby motel room.
    He mixed and cooked batches of hair bleach in the kitchenette of the motel. On the night of September 6, 2009, as he labored over the stove, Zazi sent several emails to an al Qaeda operative "Ahmad." The emails contained a well-known al Qaeda code for a terrorist operation being imminent -- "the marriage is ready" -- and also asked for specific instructions "right away, please" about the other ingredients needed for the explosive.
    Zazi had mastered the manufacture of the hair bleach-based bombs but had forgotten the precise proportions of those ingredients needed to ignite the mixture.
    If Zazi had sent these emails to an ordinary email account in Pakistan, anyone monitoring it would have assumed the query was about making a wedding cake. But the email address Zazi used to touch base with "Ahmad" was sana_pakhtana@yahoo.com, an account that was being monitored by British intelligence because someone using it had also been in touch with al Qaeda recruits in the United Kingdom.
    The Brits tipped off American officials that the email account belonged to an al Qaeda operative living in Pakistan, and the U.S. National Security Agency began monitoring it.
    Once the FBI realized there was an al Qaeda recruit living in Denver making TATP bombs, it intensively monitored Zazi. He traveled from Denver to New York to carry out his plan around the eighth anniversary of 9/11 and was soon arrested, as were two of his co-conspirators, all of whom were given long prison sentences.
    More successful for al Qaeda was the cell of British suicide bombers who carried out the "7/7" London bombings on July 7, 2005. They used their training to heat up and distill ordinary hair bleach, combining it with other ingredients to make effective bombs. Making these bleach-based bombs was a complex process, not something that could be picked up by reading bomb-making recipes on the Internet. The ringleader had received bomb-making training from al Qaeda in Pakistan.
    In an apartment the London plotters had rented to serve as their bomb factory, they mixed the chemicals. As they brewed up batches, they wore disposable masks because of the high toxicity of the materials, which bleached their dark hair a noticeably lighter color. They installed a commercial-grade refrigerator in the apartment to keep the highly unstable bomb ingredients cold. They built four devices.
    Fifty-two commuters were killed when the bombs detonated on three London Underground trains and a double-decker bus. Two weeks after the attacks, on July 21, 2005, a second wave of hydrogen peroxide-based bombs was set off in London, this one organized by a cell of Somali and Eritrean men who were first-generation immigrants to the UK. Fortunately, while four bombs were set to detonate on July 21 -- three on the Underground and one on a bus, mimicking the attacks two weeks earlier -- their faulty construction rendered them harmless.
    Hydrogen peroxide-based bombs would again be the signature of a cell of British Pakistanis who plotted to bring down seven passenger jets flying to the United States and Canada from the UK during the summer of 2006. The plotters were intent on committing suicide during the attacks on the passenger jets. Six of them made "martyrdom" videotapes recovered by British investigators.
    British authorities were tracking the ringleader intensively in the summer of 2006. When he was arrested in east London on August 10, 2006, he was carrying a memory stick storing flight plans for United Airlines, American Airlines and Air Canada jets flying from the UK to destinations such as Chicago, Washington, Los Angeles, San Francisco, Montreal and Toronto.
    Investigators later found several large bottles containing concentrated hydrogen peroxide that one of the conspirators had dumped in a London park. The plotters were planning to bring the liquid explosives disguised as soft drinks in hand luggage onto the flights they had targeted, together with other innocuous-looking items that could act as triggers. They had planned to assemble their bombs on the planes.
    It was this plot that triggered airlines to ban almost all liquids being taken on flights.
    As French investigators try to piece together what happened in Paris, they will surely be looking for where the TATP bombs were assembled, whether in an apartment as the 7/7 plotters did, or in a motel room as Zazi did, or in some other location. They will also be trying to determine who built the bombs.
    Were they built by the terrorists themselves, as was the case with the 7/7 plotters, or did someone else build them? And where did the training to build the bombs happen? Was it in France, or in Syria, or in some other location? These are some of the questions that, hopefully, the investigation will eventually unearth.
    After 9/11, the New York Police Department initiated Operation Nexus, in which cops visited thousands of stores in the city and the wider Northeast region that sold or distributed materials that could be used in a terrorist operation. It could be anything from pipes useful for pipe bombs to the explosive "black powder" that can be found in fireworks. Each store owner would be told, "If you see in an anomaly in a purchase, let us know."
    Najibullah Zazi was just such an anomaly, as he was a dark-haired, bearded Afghan-American man in his 20s who bought six bottles of Clairoxide hair bleach during one shopping trip at a store in a Denver suburb. Zazi returned to the store a month later and purchased another dozen bottles of Ms. Kay Liquid, which is also a peroxide-based hair bleach.
    It's that kind of bulk purchase of hydrogen peroxide that should trigger a suspicious activity report in the U.S. and other Western countries.