Zazi had apparently been asking his handler for help in making the explosive TATP.

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The relatively low-tech device - which contained TATP high explosive and ball bearings - was ready for use, the police spokesman said.

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Investigators found on Mr Zazi's laptop specifications for triacetone triperoxide (TATP), the explosive used in the 2005 bombings on the London Underground.

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Reid's shoes allegedly contained several bomb-related materials including the explosive PETN, plastic chemicals to gel and mold the explosives and TATP, a highly sensitive material needed to detonate the shoe bombs, sources told CNN.

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