Story highlights TATP was used in the Paris, Brussels and Manchester attacks

Many Islamist terrorists who have successfully made TATP received some training

(CNN) According to an initial assessment, traces of the powerful explosive TATP were found at the ruins of the suspected bomb factory used by the Barcelona attack cell, a source briefed on the investigation told CNN.

The source stressed the assessment was preliminary.

TATP is made by adding an acid to a mixture of acetone and hydrogen peroxide solution and can easily result in accidental detonation if mistakes are made in preparation.

It is a high explosive that is much more powerful than that used in the April 2013 Boston bombings that killed three people and wounded more than 250 others.

TATP was used in the November 2015 Paris attacks, the March 2016 Brussels bombings, the May Manchester bombing and a failed bomb attempt by an Islamist extremist at the Gare Centrale in Brussels in June.

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